The relatively lower susceptibility to malaria seen in the Fulani ethnic group in Africa, as compared to other sympatric ethnic groups, has been related to genetic regulation of the immune responses. This thesis aimed to describe important pathways related to the regulation of antibodies in the immune responses during a malaria infection. Our results suggest that the higher anti-malarial immune responses seen in the Fulani are not a general hyper-responsiveness in this group, but neither a malaria specific response. Fcγ receptors are important structures in the immune responses, and polymorphisms in these genes were associated with IgG subclass levels, P. falciparum parasitemia and haemoglobin levels, suggesting that these polymorphisms may be a contributing factor to the differential susceptibility to malaria. C-reactive protein levels rise immediately in response to inflammatory stimuli, and the -286 CRP polymorphism was indicated to influence parasite levels, suggesting a possible involvement in the lower susceptibility to malaria seen in the Fulani ethnic group. Several cytokines are important in maintaining the optimal parasite-neutralizing milieu in the host, and we investigated polymorphisms in some of these cytokine genes, in order to establish a possible influence of these on malaria susceptibility. Several of these polymorphisms showed associations with haemoglobin levels, IgG subclass antibody levels and parasitemia, suggesting that IL-1β, IL-6, IL-10 and TNF could affect the susceptibility to malaria and the severity of the malaria infection. Taken together, these data suggest that genetic factors have the ability to affect the antibody responses, and that several pathways can be affected. Moreover, the Fulani have a genetic predisposition for a higher inflammatory response during a malaria infection, which could lower their susceptibility to the disease. However, the control measures for this inflammation still have to be established and evaluated.

Rheumatoid arthritis (RA) is an autoimmune disease with systemic inflammatory features that primarily affects small peripheral joints. Type II collagen (CII), is the most abundant collagen type in joint cartilage. Antibodies against CII (anti-CII) are found in a subpopulation of RA patients. Anti-CII can form surface-bound immune complexes (IC) in inflamed joints, which might intensify joint inflammation and destruction. In this thesis I have studied the functional effects of surface-bound anti-CII–containing IC in vitro and correlated the results to clinical parameters. Anti-CII IC induced TNF-α, IL-1β and IL-8 production from monocytes via FcγRIIa. Anti-CII levels were dichotomously distributed in RA patients where a small outlier group (3.3%) with very high anti-CII levels showed in vitro induction of pro-inflammatory cytokines by anti-CII-containing IC. These patients also had a distinct phenotype with elevated laboratory signs of inflammation and increased radiological erosions at the time of diagnosis. In another in vitro model, co-cultured macrophages and RA synovial fibroblasts stimulated with anti-CII IC induced the production of matrix metalloproteinases (MMP)-1 and MMP-8, enzymes responsible for the initial cleavage of CII during cartilage degradation. This was mediated via production of TNF-α and IL-1β, and especially anti-CII IC-induced IL-1β sup-ported the production of MMP-1. The presence of anti-CII antibodies in patients with early synovitis was not predictive for future RA development. In summary, I have shown how anti-CII-containing IC may explain part of the early pathogenesis and can define a distinct clinical phenotype in RA patients with high levels of anti-CII.

Immune complexes (IC) have key pathological roles in both autoimmune and infectious diseases. In this thesis functional mechanisms behind IC-driven inflammation in rheumatic diseases and tropical infections have been studied, with special focus on the contribution of autoantibodies and cytokine-inducing properties of IC. In the autoimmune disease SLE, increased levels of IC-induced cytokines were associated with both increased classical complement activation and the occurrence of the autoantibodies anti-SSA and anti-SSB, both directed against RNA-associated antigens. In addition, complement activation and anti-SSA synergistically predisposed to higher levels of IC in sera. In the following study it was demonstrated that also other autoantibodies against RNA-associated autoantigens were more enriched than anti-dsDNA in SLE IC. Sudanese Visceral Leishmaniasis (VL) patients had elevated IC levels, and precipitated IC induced higher levels of GM-CSF, IL10, IL6 and IL1RA than control IC. Levels of IC were especially prominent in severely ill patients receiving antimony treatment, and a parallel association with IC induction of GM-CSF was demonstrated. Leishmania-infected patients were often rheumatoid factor (RF) positive and a substantial number displayed reactivity towards cyclic citrullinated peptide (CCP) antigens. Contrary to what was seen in Sudanese RA sera, the CCP reactivity was not restricted to citrulline but reacted equally well with arginine-containing control peptides. Levels of anti-CCP among VL patients were not due to cross-reactions with, or CCP-reactivity bound to IC. I have demonstrated that IC are associated with the presence of autoantibodies in both SLE and in Leishmania infection. In SLE, autoantibodies against RNA-associated antigens were more prone to form circulating IC than anti-dsDNA. In Leishmania infection false reactivity against the CCP-autoantigen correlated to IC levels although the IC themselves did not contain such reactivity. In both diseases higher IC levels were associated with a more active disease, and purified IC induced key cytokines in disease pathogeneses.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 5 uppsatser.

Malaria är ett globalt hälsoproblem som orsakar många dödsfall runt om i världen varje år och nästan hälften av jordens befolkning ligger i riskzonen att drabbas av sjukdomen. I Indien drabbas mellan 2-3 miljoner människor varje år och det inträffar omkring 900 dödsfall. Malaria orsakas av Plasmodium sp. som är en protozoe, och det finns fyra olika arter som är patogena för människor, P. vivax, P. ovale, P. falciparium samt P. malariae. Vanliga metoder för att diagnostisera malaria är genom tunna och tjocka blodutstryk som färgas till exempel med Giemsa, Fields eller Leishmans färgningsteknik och studeras mikroskopiskt, Quantitative Buffy Coat (QBC), PCR tester, acridinorange färgning samt olika immunologiska tester för detektion av antikroppar eller antigen som till exempel enzyme-linked immunosorbent assays (ELISA) test och dipstick test. Syftet med denna studie är att utvärdera om en användning av SD Bio Line Malaria Antigen ELISA kit ger en mer känslig, tillförlitlig, praktisk samt mindre kostsam diagnostikmetod för malaria hos patienter med misstänkt malariainfektion än den nuvarande guldstandardmetoden, QBC tillsammans med blodutstryk, vid Christian Medical College and Hospital i Vellore. Patientproverna har i både ELISA testet samt QBC testet tillsammans med utstryk erhållit samma resultat vilket tyder på att SD Bio Line Malaria Antigen ELISA kitet skulle kunna vara en lika bra diagnostikmetod som QBC testet för diagnos av malaria. ELISA kitet har dock fler nackdelar, i jämförelse med QBC testet, så därför är slutsatsen att SD Bio Line Malaria Antigen ELISA kitet inte är en mer lämplig diagnostisk metod för malaria än den som används vid CMCH. Men då ELISA testet ändå ger en säker diagnos, enligt resultatet i studien, kan den vara ett lämpligt test inom något annat användningsområde.

No description available.

<p>Today there are a vast number of medical devices in temporary or permanent contact with human tissues. Blood-biomaterial contact is known to trigger the complement system and results in generation of fluid phase anaphylatoxins C3a and C5a, and surface-bound C3b and iC3b. All these products together are able to attract and activate leukocytes and trigger release of inflammatory mediators leading to a systemic inflammation indirectly causing hemostatic problems and even organ failure. The aim of this study was to identify how complement is triggered on a biomaterial surface and to find ways to regulate this activation.</p><p>The finding that complement activation on biomaterials can be divided into initiation and amplification will facilitate regulation of complement activation biomaterial surfaces. This concept is also compatible with the two techniques to regulate complement activation on a surface.</p>

Today there are a vast number of medical devices in temporary or permanent contact with human tissues. Blood-biomaterial contact is known to trigger the complement system and results in generation of fluid phase anaphylatoxins C3a and C5a, and surface-bound C3b and iC3b. All these products together are able to attract and activate leukocytes and trigger release of inflammatory mediators leading to a systemic inflammation indirectly causing hemostatic problems and even organ failure. The aim of this study was to identify how complement is triggered on a biomaterial surface and to find ways to regulate this activation. The finding that complement activation on biomaterials can be divided into initiation and amplification will facilitate regulation of complement activation biomaterial surfaces. This concept is also compatible with the two techniques to regulate complement activation on a surface.

Lymphocytes, the principal cells of the immune system, perform the immune function throughout the body by their unique capacity to circulate in blood stream and lymphatic vessels and migrate in lymphoid and non-lymphoid tissues. The mechanisms regulating lymphocyte adhesion and migration, interactions with cells and components within the extracellular matrix are not fully understood. The aim of this work has been to elucidate molecular mechanisms governing T lymphocyte adhesion and migration by endogenous molecules. The studies presented in this thesis have shown that thrombospondin-1 (TSP-1) is expressed in T lymphocytes with a high turnover, manifested by variable cell surface expression, and is regulated by SDF-1a, adhesion to fibronectin and collagen type IV. The TSP-1 binding site of calreticulin (CRT), spanning amino acid 19-32, was shown to be a major triggering factor for T cell migration within a three-dimensional collagen type 1 matrix. The chemokine SDF-1a stimulated migration via a calreticulin-TSP-1 pathway. Endogenous calreticulin binding to the N-terminal domain of endogenous TSP-1 elicited a motogenic signal to the T cells through the C-terminal domain of TSP-1 and its cell surface receptor integrin-associated protein (IAP, CD47). Inhibition experiments of ligand binding of CD91 by receptor associated protein (RAP) and small interfering RNA technology indicated that CD91 is an important factor in TSP-1-mediated T cell adhesion and migration. These results unveil an autocrine mechanism of CRT-TSP-1-CD47-CD91 interaction for the control of T cell motility and migration within 3D extracellular matrix substrata. The data demonstrated that T cell adhesion and migration are sequential events governed by a series of interacting cell surface molecules comprising a CRT-TSP-1-CD47-CD91 pathway where endogenous TSP-1 functions as the hub. Ligation of the CD3/T cell antigen receptor complex determines T cell adhesion through this mechanism. CRT interaction with the N-terminal domain of TSP-1 elicits cytoplasmic spreading, and augments adhesion, while a counter-adhesive motogenic pathway, triggering interaction of the C-terminal domain of TSP-1, induces migration. CD91-dependent internalization of TSP-1 is a crucial event of this motogenic pathway. In conclusion, the studies provide a novel mechanism governing T cell adhesion and migration within extracellular matrix substrata.

No description available.