In recent decades the number of children with overweight has increased worldwide. To understand the mechanisms behind this development, knowledge regarding metabolism and physiology in relation to the nutritional situation in early life is of importance. In particular, information about body composition development during early childhood is relevant. This thesis presents three studies in this area. In the pregnancy study serum samples, collected from 23 women before, during and after pregnancy, were analysed for serum levels of leptin, adiponectin and resistin and used to assess insulin resistance (HOMA-IR) in relation to the total body fat (TBF) content of the women. TBF (%) and leptin were significantly correlated with HOMA-IR before and during pregnancy. When HOMA-IR was regressed on TBF (%) the slope of the regression line was 0.111 in gestational week 32 and significantly (p<0.05) higher than the value before pregnancy, 0.046, indicating that healthy pregnancy enhances the relationship between body fatness and insulin resistance. In the HF-study hydration of fat-free mass (hydration factor, HF) was assessed in 12 newborns using the doubly labelled water (DLW) method and air displacement plethysmography (PeaPod). HF was 80.9% with a low biological variability (0.81% of average HF). In the longitudinal study the body density of 108 healthy fullterm infants (53 girls, 55 boys) was measured at one and 12 weeks of age using PeaPod. Body composition was calculated using two models (Fomon’s and Butte’s). BMI values for the mothers of the infants were assessed before pregnancy. Body composition and total energy expenditure using the DLW-method were assessed in 20 of these children at the age of 1.5 years, when their sleeping metabolic rate was measured using indirect calorimetry and their resting energy metabolism was calculated using prediction equations. Butte´s model gave significantly (p<0.05) lower values for TBF than Fomon´s model, and invalid results for five newborns. Using Fomon´s model, at one week of age girls contained 13.4 ± 3.7 % and boys contained 12.5 ± 4.0 % TBF. The corresponding figures at 12 weeks were 26.3 ± 4.2 % and 26.4 ± 5.1 %. The mothers’ BMI values before pregnancy were correlated with the body weight but not with the TBF (g,%) or fat-free mass (g) of their infants at one week of age. At 1.5 years of age girls (n=9) contained 28.0±2.8 % and boys (n=11) 28.3±3.7 % TBF. Between one and 12 weeks of age all infants increased their TBF content, while 13 children increased and seven children decreased their TBF content between the ages of 12 weeks and 1.5 years. The results demonstrated that predicting rather than measuring resting energy metabolism involves a risk for spurious correlations between TBF and physical activity level. The level of physical activity (x), was negatively correlated with [TBF (%) at 1.5 years minus TBF (%) at 12 weeks] (y), r=-0.52, p=0.02. In conclusion, the results suggest that the body fat content of a woman has a stimulating effect on the growth, rather than on the fat retention, of her foetus. They also show that the Fomon model is the best available model when calculating the body composition of infants from body density. Finally, the results indicate that physical activity at the age of 1.5 years is important regarding the rate at which the high level of body fat, typical of infancy, decreases in early childhood. / Övervikt och fetma bland barn har under senare år blivit allt vanligare i många delar av världen. Studier av nutrition, metabolism och fysiologi under graviditet och de tidiga barnaåren är av vikt för att förstå vilka faktorer som ligger bakom denna utveckling. Speciellt viktigt är att studera hur kroppssammansättningen förändras tidigt i livet. Den här avhandlingen innehåller tre studier som berör detta ämnesområde. I en studie på gravida analyserades serumprover, insamlade från 23 kvinnor innan, under och efter deras graviditet, med avseende på halter av leptin, adiponektin och resistin. Via serumproverna fastställdes också kvinnornas insulinresistens (HOMA-IR). Dessa resultat relaterades sedan till mängden kroppsfett hos dessa kvinnor. Mängden kroppsfett (%) och leptin visade, före och under graviditet, en signifikant korrelation med HOMA-IR. En regressionsanalys av HOMA-IR (y) och % kroppsfett (x) i graviditetsvecka 32 gav ett k-värde (lutning) på 0,111, vilket i jämförelse med motsvarande k-värde före graviditet 0,046 var signifikant högre (p<0.05). Detta resultat visar att hos friska kvinnor potentierar graviditeten sambandet mellan kroppsfett och insulinresistens. I en studie av hydreringsgrad i fettfri kroppsvikt (HF) fastställdes HF i 12 nyfödda med hjälp av dubbelmärkt vatten och helkroppsplethysmografi (PeaPod). HF uppmättes till 80,9% med en låg biologisk variation (0,81 % av genomsnittlig HF). I en longitudinell studie mättes kroppsdensiteten med PeaPod hos 108 friska fullgångna spädbarn (53 flickor, 55 pojkar) när de var en respektive tolv veckor gamla. Deras kroppssammansättning beräknades med två olika modeller (Fomons och Buttes). Uppgift om mödrarnas pregravida BMI samlades in. Vid 1,5 års ålder mättes kroppssammansättning och total energiomsättning hos 20 av de 108 barnen. Vid detta tillfälle mättes även viloomsättningen med indirekt kalorimetri under sömn. Viloomsättningen predikterades även med en formel. Buttes modell gav signifikant (p<0.05) lägre nivå av kroppsfett (%) jämfört med Fomons modell och i fem fall erhölls inga resultat alls. Beräkningar med Fomons modell visade att vid en veckas ålder innehöll flickorna 13.4 ± 3.7 % och pojkarna 12.5 ± 4.0 % kroppsfett. Motsvarande värden vid 12 veckors ålder var 26.3 ± 4.2 % och 26.4 ± 5.1 %. Mödrarnas BMI innan graviditet korrelerade med kroppsvikt men inte med kroppsfett (g,%) eller fettfri vikt (g) hos deras barn vid en veckas ålder. Vid 1,5 års ålder innehöll flickorna (n=9) 28.0±2.8 % och pojkarna (n=11) 28.3±3.7 % kroppsfett. Mellan en och 12 veckors ålder ökade alla barnen sin kroppsfetthalt. Mellan 12 veckor och 1,5 år ökade kroppsfetthalten hos 13 barn medan den minskade hos 7. Resultat visar att predikterad viloomsättning ökar risken för att få en falsk korrelation mellan kroppsfetthalt och fysisk aktivitetsnivå jämfört med om man använder uppmätt viloomsättning. Den fysiska aktivitetsnivån vid 1,5 års ålder (x), var negativt korrelerad till förändring i kroppsfetthalt [kroppsfett (%) vid 1.5 år minus kroppsfett (%) vid 12 veckor] (y), r=-0.52, p=0.02. Sammanfattningsvis tyder resultaten på att kvinnors kroppsfetthalt har en stimulerande effekt på fostrets på totala tillväxt men inte på dess retention av kroppsfett. Dessutom visar resultaten att Fomons modell är den bästa tillgängliga när det gäller att beräkna kroppssammansättningen hos spädbarn från kroppsdensitet. Slutligen tyder resultaten på att den fysiska aktivitetsnivån vid 1,5 års ålder har betydelse för hur fort den höga kroppsfetthalten, som är typisk för spädbarnsperioden, sjunker under tidig barndom.

In the years 1995 to 2001, 970 women with urinary incontinence underwent surgery with tension-free vaginal tape (TVT) at the Department of Obstetrics and Gynecology, Falun Hospital. In 2002 the charts of all these women were reviewed and a questionnaire was sent in 2004. 760 women (78,4%) answered the questions. The mean time since surgery was 5.7 years. The mean age at surgery was 58.7 years. Of all patients, 580 had pure stress urinary incontinence (SUI) and 112 had mixed urinary incontinence (MUI) prior to surgery. Of the women with SUI, 85 % were subjectively and persistently cured. Of the women with MUI, 60 % were subjectively cured up to 3 years after the TVT operation.  However this figure declined to 30 % among women operated on 6-8 years previously. The increasing incontinence was due to urgency symptoms and urge urinary incontinence (UUI).The IIQ-7 and UDI-6 questionnaires were used for measuring quality of life. The women showed dramatic improvement after TVT surgery irrespective of time since surgery. Women with chronic diseases also had relative improvement in QOL scores. Sixty-seven of the women with pure SUI preoperatively (14.5%) reported persistent de novo urgency symptoms postoperatively and 51 of the women also had UUI. Old age, history of cesarean section, increasing parity and BMI were risk factors for developing de novo urgency after TVT procedure. Among women ≥ 75 years 55.7% reported cure after TVT, compared to 79.7% of women < 60 years. The overall cure rate in the very overweight women (BMI ≥ 35) was 52.1%, compared to 81.2% in women of normal weight (BMI < 25). Conclusions. The subjective results after TVT surgery for SUI are very good even after 8 years. Short-term effect of TVT on MUI is acceptable, but declines after 3 years. Improvements in measures of quality of life after TVT surgery are dramatic and persistent in both the SUI and MUI groups. Women who developed de novo urgency symptoms after TVT surgery reported poorer quality of life. The TVT procedure is simple and safe, but the results in the oldest or most overweight women are not as good as in the younger or normal weight women.

Low back pain consumes a large part of the community’s resources dedicated to health care and sick leave. Back disorders also negatively affect the individual leading to pain suffering, decreased quality-of-life and disability. Chronic low back pain (CLBP) due to degenerative disc disease (DDD) is today often treated with fusion when conservative treatment has failed and symptoms are severe. This treatment is as successful as arthroplasty is for hip arthritis in restoring the patient’s quality of life and reducing disability. Even so, there are some problems with this treatment, one of these being recurrent CLBP from an adjacent segment (ASD) after primarily successful surgery. This has led to the development of alternative surgical treatments and devices that maintain or restore mobility, in order to reduce the risk for ASD. Of these new devices, the most frequently used are the disc prostheses used in Total Disc Replacement (TDR). This thesis is based on four studies comparing total disc replacement with posterior fusion. The studies are all based on a material of 152 patients with DDD in one or two segments, aged 20-55 years that were randomly treated with either posterior fusion or TDR. The first study concerned clinical outcome and complications. Follow-up was 100% at both one and two years. It revealed that both treatment groups had a clear benefit from treatment and that patients with TDR were better in almost all outcome scores at one-year follow-up. Fusion patients continued to improve during the second year. At two-year follow-up there was a remaining difference in favour of TDR for back pain. 73% in the TDR group and 63% in the fusion group were much better or totally pain-free (n.s.), while twice as many patients in the TDR group were totally pain free (30%) compared to the fusion group (15%). Time of surgery and total time in hospital were shorter in the TDR group. There was no difference in complications and reoperations, except that seventeen of the patients in the fusion group were re-operated for removal of their implants. The second study concerned sex life and sexual function. TDR is performed via an anterior approach, an approach that has been used for a long time for various procedures on the lumbar spine. A frequent complication reported in males when this approach is used is persistent retrograde ejaculation. The TDR group in this material was operated via an extra-peritoneal approach to the retroperitoneal space, and there were no cases of persistent retrograde ejaculation. There was a surprisingly high frequency of men in the fusion group reporting deterioration in ability to have an orgasm postoperatively. Preoperative sex life was severely hampered in the majority of patients in the entire material, but sex life underwent a marked improvement in both treatment groups by the two-year follow-up that correlated with reduction in back pain. The third study was on mobility in the lumbar spinal segments, where X-rays were taken in full extension and flexion prior to surgery and at two-year follow-up. Analysis of the films showed that 78% of the patients in the fusion group reached the surgical goal (non-mobility) and that 89% of the TDR patients maintained mobility. Preoperative disc height was lower than in a normative database in both groups, and remained lower in the fusion group, while it became higher in the TDR group. Mobility in the operated segment increased in the TDR group postoperatively. Mobility at the rest of the lumbar spine increased in both treatment groups. Mobility in adjacent segments was within the norm postoperatively, but slightly larger in the fusion group. In the fourth study the health economics of TDR vs Fusion was analysed. The hospital costs for the procedure were higher for patients in the fusion group compared to the TDR group, and the TDR patients were on sick-leave two months less. In all, these studies showed that the results in the TDR group were as good as in the fusion group. Patients are more likely to be totally pain-free when treated with TDR compared to fusion. Treatment with this new procedure seems justified in selected patients at least in the short-term perspective. Long-term follow-up is underway and results will be published in due course.

Colorectal cancer is a major cause of morbidity and mortality around the world, each year affecting about one million individuals worldwide. The disease is characterized by an accumulation of genetic alterations, and a sequence of events leading to the development of an invasive and metastasising tumour. Chronic or dysregulated inflammation may contribute to tumour initiation and progression via the release and activity of various mediators – e.g. cytokines, prostaglandins, inducible nitric oxide synthase (NOS2), matrix metalloproteinases (MMPs), and vascular endothelial growth factors (VEGF). In the present thesis, genes and genetic alterations controlling these events were analysed and discussed within the context of colorectal cancer. Prostaglandins, being generated from arachidonic acid in reactions dependent on cyclooxygenases (COX-1, COX-2), have been implicated in carcinogenesis of many organs. Since the quite recent characterization of the terminal and specific prostaglandin synthases, which act downstream of COX enzymes, the search for molecular targets which selectively suppress individual prostanoids has been intensified. In papers I-II, the role and regulation of inducible prostaglandin E2 (PGE2) synthase - mPGES-1 - were explored within the context of intestinal cancer. mPGES-1 was genetically deleted in the ApcMin/+ mouse - yielding marked suppression of PGE2 generation in intestinal and tumour tissue. However, a shift towards enhanced generation of non-PGE2 prostanoids was observed in mPGES-1 knock out mice, and these mice developed more and larger instestinal tumours. These results therefore indicate that targeting mPGES-1 may paradoxically promote tumourigenesis, most likely by secondary effects on other potentially pro-tumoural mediators. We also explored the relation of the commonly mutated APC gene and mPGES-1 in colon tumour cells, and found that high expression of mPGES-1 was associated with the presence of wild type APC. Rather than by regulating putative β-catenin/Tcf binding sites of the mPGES-1 promoter, APC seems to influence the stabilisation of mPGES-1 mRNA. In papers III-V, the possible contribution of variations in regulatory regions of genes encoding NOS2, MMPs, and VEGF, was assessed in populations of colorectal cancer patients and healthy control individuals. A single nucleotide insertion (1G/2G) at -1607 upstream the transcription start site of the MMP-1 gene was identified to be a susceptibility factor for colorectal cancer development, although no relation with disease characteristics was observed. Except for a rather uncommon combination of two individual polymorphisms of the VEGF gene, investigated genetic variations of VEGF, other MMPs, and NOS2, were not associated with colorectal cancer susceptibility or clinicopathological characteristics. We therefore suggest that other molecular events play more significant roles for the dysregulation of these genes in colorectal tumours. In summary, accumulating evidence, including the results here presented, suggest significant albeit complex roles of inflammation-induced genes and mediators in colorectal tumourigenesis. The present results may aid in identifying or excluding potential biomarkers and drug targets within cancer-related inflammation.

Background: The incidence of allergic diseases in industrialized countries has increased, and a relation between allergy and dietary fatty acids has been proposed. Modulation of the maternal immune function during pregnancy may have an impact on future clinical outcome in the child. Aim: The aim of this thesis was to add knowledge on the relationship between long chain polyunsaturated fatty acids, sensitization and allergic disease and possible immunological events regulating this. Subjects: The thesis is based on results obtained from two cohorts. The first, including 300 cord blood samples collected from 1985-2005. The second, a double-blind placebo controlled multi-centre study comprising 145 families with allergic disease. Methods: Phospholipid fatty acids and total IgE antibodies were analyzed in cord blood samples with gas chromatography and Uni-CAP™, respectively. The families participating in the double-blind placebo controlled multi-centre study were recruited at antenatal units in Linköping and Jönköping and the mothers were supplemented with 2.6 g ω-3 long-chain polyunsaturated fatty acids (LCPUFA) or placebo daily from gestational week 25 until 3 months of breast feeding. Phospholipid fatty acids in maternal serum were analysed before and during the intervention to assess compliance. Prostaglandin E2, leukotrienes B4 and cytokines were analyzed with ELISA technique in supernatants from maternal LPS-stimulated whole blood cultures. Clinical outcome was allergic disease with positive skin prick test and/or specific circulating IgE to food allergens at one year of age. Cytokines, chemokines, SIgA antibodies and prostaglandin E2 were analyzed in breast milk with Luminex and ELISA techniques. Results: The proportions of cord serum linoleic acid (LA, C18:2 ω-6) and α-linolenic acid (LNA, C18:3 ω-3) decreased significantly from 1985 to 2005. However, the LA/LNA ratio did increase, revealing a relatively larger decrease in LNA than in LA. The proportions of both arachidonic acid (AA; C20:4 ω-6) and docosahexaenoic acid (DHA, C22:6 ω-3) as well as other ω-6 and ω-3 fatty acids increased significantly during the same time period. No correlations were found between ω-6 and ω-3 fatty acids and total IgE antibodies. Proportions of ω-3 LCPUFA increased in the ω-3 supplemented group of mothers. Lipopolysaccharide-induced prostaglandin E2 secretion in whole blood culture decreased in a majority of ω-3 PUFA supplemented mothers (18 of 28, p < 0.002).The decreased prostaglandin E2 production was more pronounced among non-atopic than atopic mothers. Lipopolysaccharide induced cytokine and chemokine secretion was not affected. The period prevalence of food allergy was lower in the ω-3 group (1⁄52, 2%) compared to the placebo group (10⁄65, 15%, p <0.05) as well as the incidence of IgE-associated eczema (ω-3 group: 4 ⁄ 52, 8%; placebo group: 15 ⁄ 63, 24%, p < 0.05) at one of year. There were no differences in breast milk cytokine, SIgA and PGE2 levels between the two intervention groups. However, the levels of several cytokines tended to be higher in colostrum from non-atopic ω-3 supplemented mothers as compared to non-atopic placebo supplemented mothers. Higher levels of TGFß2 and SIgA in 3 months milk were associated with allergic disease at one year of age both with and without detectable IgE. Conclusions: Cord blood LA proportions decreased and LA/LNA ratio increased over the 20 year period between 1985 and 2005 this was not related to total IgE. ω-3 fatty acid supplementation of pregnant and lactating mothers resulted in a lower period prevalence of IgE associated eczema and food allergy in the children at one year of age. This was most pronounced in children of non-allergic mothers. The underlying mechanism requires further clarification.

Carcinogenesis is a sophisticated biological process consisting of a series of progressive changes in somatic cells from premalignant to malignant phenotype. Despite the vast information available about cancer cells, the origin of cancer and cause of metastasis still remain enigmatic. The hypothesis of cell fusion is one of several models explaining the evolution of neoplasia into clinically significant cancer. This theory states that cancer cells through heterotypic fusion with host cells generate hybrids expressing traits from both parental cells, and acquire metastatic potentials and growth-promoting properties. The cell fusion theory is still unproven and speculative, but cell fusion is a common biological process in normal tissue. Accumulated evidence shows that macrophage-cancer cell fusion occurs in vitro and in vivo and produces hybrids with metastatic potential, but the clinical significant of cell fusion is unclear. The aim of this thesis is to test this hypothesis in clinical patient materials and to explore the clinical significance of macrophage phenotype traits in solid tumours. Paraffin-embedded cancer and normal tissue specimens from patients with breast cancer (n=133) and colorectal cancer (two different patient materials with totally 240 patients) were immunostained for the macrophage-specific antigen, CD163. The expression of CD163 was tested in relation to macrophage infiltration and tumour stage, survival time, irradiation, DNA ploidy, cancer cell proliferation and apoptosis. Phenotypic macrophage traits, such as the expression of CD163, were seen in both breast and colorectal cancers, and were correlated to advanced tumour stages and poor survival. CD163 expression was more frequent in rectal cancer after irradiation and was associated with decreased apoptosis. Cancer cell proliferation was correlated to both macrophage infiltration and CD163 expression. Multivariate analysis showed that CD163 is a significant prognostic factor in both breast and colorectal cancers. In an attempt to examine factors related to the function of macrophage fusion, the expression of the signalling adaptor protein DAP12 was tested and related to CD163 expression in breast cancers from 133 patients. DAP12 was shown to occur in breast cancer cells and was related to high histologic tumour grade, skeletal and liver metastasis, and poor prognosis. The findings in this thesis support the cell fusion theory and illustrate its clinical impact on tumour progression and metastasis.

The Gram-positive cocci, Staphylococcus aureus, coagulase negative staphylococci (CoNS), Enterococcus faecalis and Enterococcus faecium, are the bacteria most often isolated from patients with hospital acquired infections. S. aureus is one of the most important pathogens and have a variety of virulence mechanisms which help it to infect the patient and cause tissue damage. CoNS and enterococci are low virulent bacteria and predominantly cause infections in individuals with underlying illness, individuals that have undergone surgery or with suppressed immune-system. The aims of this thesis were i) to investigate the susceptibility to different antimicrobial agents among S. aureus, CoNS, E. faecium and E. faecalis isolates from primary care centres, general hospital wards and intensive care units in Denmark, Finland, Norway and Sweden and ii) to study the prevalence of the cytolysin genes and genes involved in biofilm formation among CoNS, E. faecium and E. faecalis. The results in this thesis show that the resistance rates among S. aureus and E. faecalis is still rather low in the north European countries. Among CoNS and E. faecium resistance rates are higher and comparable with rates in other European countries and US. CoNS had statistically significant differences in susceptibility rates between the ward levels with the lower susceptibility rates found at ICUs. Continued surveillance of resistance rates to antimicrobial agents among both staphylococci and enterococci are important internationally, nationally and locally. The results in this thesis also show that all multidrug resistant and 96% of the susceptible CoNS isolates carried at least one of the atlE and aap genes or the ica operon. Among E. faecalis isolates with HLGR, belonging to a cluster of genetically related isolates, both the esp and asa1 genes were carried in a high degree while the cyl operon was less frequently found. In addition, about 30% of unique E. faecalis isolates carried two or more of the virulence genes. Among E. faecium isolates the esp gene was common but asa1 and the cyl operon was not found in any of the isolates. Both CoNS and E. faecalis isolates from hospitalised patients are well equipped with genes involved in biofilm formation. These genes, when expressed and even more in combination with resistance to antimicrobial agents, might give these isolates an advantage compared to other isolates when it comes to adhesion to artificial surfaces, persistence in the hospital environment, colonisation of hospitalised patients and to cause nosocomial infections. Further studies are needed to be able to determine which isolates that causes hospital acquired infections and to evaluate the importance of the genes involved in biofilm formation as virulence factors and about how to prevent biofilm related infections from emerging

The general aim of this thesis was to prospectively examine the effects on health and well-being when healthy normal weight individuals increase their energy intake, mainly from fast food and simultaneously adopt a sedentary lifestyle. This thesis is based upon a prospective experimental study design where 18 healthy normal weight individuals, 12 men and 6 women, aged 26 (6.6) years, increased their energy intake with in average 70 % during four weeks. Simultaneously their physical activity was limited to a maximum of 5000 steps per day. An age and gender matched control group (n=18), was recruited and asked not to change their eatingand physical activity habits for four weeks. Long-term follow-up measurements were performed after 6 and 12 months and 2.5 years after the intervention. During the intervention body weight increased with 6.4 (2.8) kg and measurements of body composition showed an increase of both fat mass and fat free mass after the intervention. Lower physical and mental health scores on SF-36 as well as depressive symptoms were found compared to baseline. They were temporary and when followed up 6 and 12 months after the intervention, physical and mental health had returned to baseline values, despite a somewhat increased body weight. The main essence of adopting an obesity provoking behaviour was lack of energy emerging from five structures: influenced self-confidence, commitment to oneself and others, managing eating, feelings of tiredness and physical impact. Laboratory measurements showed an increase of ALT above reference limits in 14 of the 18 participants during the intervention and HTGC increased, although this was not related to the increase in ALT levels. Twelve months after the intervention an increase of body weight with 1.5 (2.4) kg was found compared to baseline (p=0.018), fat free mass was unchanged compared to baseline while fat mass had increased, + 1.4 (1.9) kg (p=0.01). Two and a half years after the intervention an increase of body weight with 3.1 (4.0) kg was found compared to baseline (p=0.01), while there was no change in controls compared to baseline, + 0.1 (2.5) kg (p=0.88). Hyper-alimentation and limited physical activity during a short-term period of 4 weeks is sufficient to temporarily induce worsened HRQoL, cause depressive symptoms and lack of energy in healthy normal weight individuals. There were also temporary but clear effects on biochemical markers, suggesting that hyperalimentation per se can induce profound ALT elevations in less than 4 weeks. During the intervention both fat mass and fat-free mass increased while after 12 months there was only an increase of fat mass which was greater than expected from epidemiological studies. The marked difference between the increase in body weight in the intervention- and control group at 2.5 years also raises the question whether there is a long-term effect of increasing fat mass after a short period of hyperalimentation.

Background: A connection has been proposed between the increase of allergic disease and the altered composition of fatty acids in the diet in the westernised world. Less oily fish and more vegetable oil are consumed today compared to 50-100 years ago. Programming of the immune responses takes place very early in life and environmental factors, such as fish in the diet, have been suggested to protect from infant allergy. Aim: The general aim of this thesis was to assess the effects of maternal dietary supplementation with ω-3 long chain polyunsaturated fatty acids (LCPUFA), i.e. fish oil, in pregnancy and lactation on the development of allergic symptoms and sensitisation in the infants as well as some immunological markers in mothers and infants. Subjects and methods: This thesis is based on the results from a prospective double-blind placebo-controlled multi-centre trial comprising 145 families. Pregnant women, at risk of having an allergic infant, were recruited at the antenatal clinics and randomised to daily supplementation with 1.6 g eicosapentaenoic acid (EPA, C20:5ω-3) and 1.1 g docosahexaenoic acid (DHA, C22:6ω-3) or placebo, starting in the 25th gestational week and continuing through 3.5 months of breastfeeding. Phospholipid fatty acids in maternal and infant plasma were analysed to assess compliance. Maternal prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and cytokines along with infant vaccine induced responses and chemokines were analysed with ELISA and Luminex techniques. Clinical outcomes were allergic disease and positive skin prick test/detectable circulating IgE antibodies to common allergens. Results: Phospholipid proportions of ω-3 LCPUFA increased significantly in the ω-3 supplemented women and their infants. Lipopolysaccharide-induced PGE2 secretion from whole blood culture supernatants decreased in a majority of the ω-3-supplemented mothers (p<0.01). The decrease in PGE2 production was more pronounced among non-atopic than atopic mothers. No difference in the prevalence of allergic symptoms was found between the intervention groups. The cumulative incidence of IgE associated eczema and IgE mediated food allergy was though reduced in the ω-3 group during the first two years (OR=0.2 and 0.3 compared to placebo, p<0.05 for both). The cumulative incidence of any IgE associated disease during the first two years of life was 13% in the ω-3 supplemented group compared to 30% in the placebo group (p=0.01, OR 0.3, p<0.05). This effect was most evident in infants of non-allergic mothers. Higher maternal and infant proportions of DHA and EPA were associated with lower prevalence of IgE associated disease (p=0.01-0.05), in a dose dependent manner. In addition, no allergic symptoms as compared to multiple allergic symptoms in the infants, regardless of sensitisation, were related to higher maternal and infant ω-3 LCPUFA status (p<0.05). In infants without, but not with, maternal history of allergy, the ω-3 supplementation was related to lower CC-chemokine ligand 17 (CCL17)/ CXC-chemokine ligand 11 (CXCL11) (Th2/Th1) ratios (p<0.05). Furthermore in non-allergic, but not in allergic infants, ω-3 supplementation was linked with higher Th1-associated CXCL11 levels (p<0.05), as well as increased IgG titres to diphtheria (p=0.01) and tetanus (p=0.05) toxins. Conclusions: A decreased cumulative incidence of IgE associated disease in the infants was found after maternal ω-3 LCPUFA supplementation as well as a reverse dose response relationship between maternal ω-3 LCPUFA status and infant IgE associated disease. Higher plasma proportions of DHA and EPA in were also associated to less severe allergic disease. A tendency towards strengthened Th1 associated response after maternal ω-3 LCPUFA supplementation was indicated in the analysis of maternal and infant immunological markers. These effects, as well as the clinical outcomes, were more pronounced in non-allergic individuals, suggesting gene-by-environment interactions.

The hematopoietic system is a highly dynamic organ developed in many multi-cellular organisms to provide oxygen, prevent bleeding and to protect against microorganisms. The blood consist of many different specialized cells that all derive from rare hematopoietic stem cells (HSCs) located in the bone marrow in mice and humans. Blood cell production from HSCs occurs in a stepwise manner through development of intermediate progenitors that gradually loose lineage potentials. This is a tightly regulated process with complex regulatory mechanisms and many checkpoints that ensure a high and balanced production of blood cells. One of the fundamental questions in hematopoiesis relates to how the maturation of the cells is controlled and driven towards defined cell fates. The understanding of these processes is largely facilitated by isolation of intermediate populations of cells at defined stages of development. This thesis is focused on the regulatory mechanisms that regulate the maturation of B-lymphocytes constituting an important part of adaptive immunity by being responsible for the production of antibodies. It has been suggested that all the lymphoid cells have a common lineage restricted ancestor defined as a Lin-KitloSca1loFlt3+IL7R+ common lymphoid progenitor (CLP). These cells are believed retain the combined potentials for B, T and NK cells and it has been presumed that commitment of CLPs to B lineage is associated with expression of CD19 and B220 on progenitor B-cells. The aim of this thesis has been to identify the point of no return in B-cell development in order to allow for a better understanding of lineage restriction events in early lymphopoesis. To this end, we have used reporter transgenic mice where marker gene expression has been controlled by the transcription regulatory elements from one early lymphoid marker (Rag1) and one B-lymphoid restricted gene (λ5, Igll1). This allowed us to identify three functionally distinct sub-populations within the conventional CLP compartment. The cells were identified as CLPRaglowλ5- cells retaining B, T, Nk and a limited myeloid potential while up-regulation of Rag1 to generate CLPRaghighλ5- cells, was associated with loss of Nk potential as well as of the residual myeloid potential. Ultimately expression of λ5 in the CLPRag1highλ5+ compartment identifies the first committed B cells. Hence, our data suggest that the point of no return in B-cell development can be found within the CD19- CLP compartment. Using this new model for B-cell development, we investigated the instructive vs. permissive role of IL7 signaling in B cell commitment. Our results show that in absence of IL7, CLP maturation is impaired and generation of the earliest committed B-lineage cells is severely impaired. CLP maturation could not be rescued by ectopic expression of the anti-apoptotic Bcl2 protein even though the cells were able to generate normal B lineage cells after restoration of the IL7 signal. These findings suggest that Il7 is crucial for the maturation of lineage restricted CLPs and provide support for an instructive role of IL7 in early Bcell development. This thesis highlights the importance of precise identification of the point of commitment in B cell development and provides insight to the hematopoietic hierarchical model with the potential to serve as a map to better understand the mechanisms of hematopoietic disorders.