Plasma cells, the effector stage of the B cell compartment, secrete large amounts of antibody. These cells arise in two waves during T-­‐dependent immune responses; an early wave (extrafollicular plasma cells) generate low-­‐affinity antibodies that provide a first line of defence against invading pathogens. Later, plasma cells emerge from the germinal centre reaction and secrete high-­‐affinity antibodies. These plasma cells have the capacity to migrate to the bone marrow, where they become established as long-­‐lived, non-­‐dividing plasma cells. Here, I show that plasma cells found in the bone marrow of young (5-­‐week-­‐old) mice had a turnover comparable to that seen in the spleen. Long-­‐lived plasma cells accumulated over the ensuing weeks until they came to dominate the bone marrow plasma cell compartment by 30-­‐weeks of age. This accumulation required MHC II, CD40 and a normal B cell receptor repertoire, implying that these cells are generated during T-­‐dependent immune responses. Secondly, I determine the signalling pathways required to generate splenic extrafollicular plasma cell responses in the T-­‐dependent response to sheep red blood cells (SRBC) and in bacterial infection with Salmonella. While T cell help, antigen recognition through the B cell receptor (BCR) and TLR signalling were required for maximal plasma cell responses to SRBC, in Salmonella infection TLR signalling was required for day 4 IgM plasma cell responses, whereas class-­‐ switched responses at day 8 required T cell help. The extrafollicular responses generated in Salmonella persisted for around 35 days, far greater than the 2-­‐3 days seen following SRBC immunisation. This was likely due to both antigen persistence causing the generation of new plasma cells, and the induction of cellular populations that produced the plasma cell survival factor APRIL. Thirdly, I document the failure of chronic immune responses to generate long-­‐ lived bone marrow plasma cells. This was accomplished by measuring the generation and survival of bone marrow plasma cells in models of rheumatoid arthritis (K/BxN mice), long-­‐term infection with Salmonella, and a direct comparison between acute and chronic delivery of the T-­‐dependent protein antigen NP-­‐KLH. In all cases, chronic immune responses generated few bone marrow plasma cells, ostensibly due to a failure to migrate to the organ. Finally, I show the depletion of bone marrow plasma cell populations caused by inflammatory episodes. This was observed in Salmonella infection, Schistosoma mansoni infection and immunisation with protein antigen plus adjuvants. This depletion mediated a reduction of antigen-­‐specific bone marrow plasma cell populations and serum antibody previously established by the secondary response to NP-­‐KLH.

Prolonged periods of non-weightbearing activity result in a significant loss of bone mass which increases the risk of fracture with the initiation of mechanical loading. The loss of bone mass is partially driven by declines in bone formation yet the mechanisms responsible for this decline are unclear. To investigate the limitations of osteoblasts during disuse, marrow ablation was superimposed on hindlimb unloaded mice. Marrow ablation is a useful model to study osteoblast functionality as new cancellous bone is rapidly formed throughout the marrow of a long bone while hindlimb unloading is the most common method used to produce skeletal unloading. The specific hypotheses of this study were aimed at determining if changes in osteoblast functionality, differentiation, and/or proliferation were compromised in non-weightbearing bone in response to a bone formation stimulus. Additionally, the influence of having compromised osteoblast functionality at the time of stimulation was assessed in non-weightbearing bones. Key outcome measures used to address these hypotheses included static and dynamic cancellous bone histomorphometry, bone densitometry, and real-time polymerase chain reaction (PCR) analyses of gene expression. The results document similar ablation-induced increases of cancellous bone in both weightbearing and unloaded animals. Similarly, there was no influence of load on ablation-induced increases in cancellous bone forming surface or mineral apposition rate. Unloading did significantly attenuate the ablation-induced increase in bone formation rate, due to reduced levels of total surface mineralization. When osteoblast functionality was compromised prior to marrow ablation, bone formation rate increases were also attenuated in ablated animals due to reduced mineralization. Additionally, increases in forming surface were attenuated as compared to unloaded animals having normal osteoblast function at the time of ablation. Collectively, these data identify mineralization as the limiting step in new bone formation during periods of disuse. The caveat, however, is that when bone formation is stimulated after a period of unloading sufficient to compromise osteoblast functionality, increases in osteoblast recruitment to the bone surface are compromised.

Bone marrow transplantation (BMT) is the treatment of choice for many malignancies and other childhood disorders. Acknowledging that the entire family is affected when a child undergoes a BMT, increasing research attention has been given to understanding this experience from the perspectives of recipients, parents and the family as a whole. Yet, minimal attention has been directed at understanding the experience of healthy siblings as they transition through the BMT experience. Before intervention studies can be undertaken that will help healthy siblings transition through the BMT experience, knowledge about the impact of the experience on siblings is needed. Accordingly, a qualitative study guided by the philosophy of hermeneutic phenomenology was conducted to elicit detailed descriptions of the lived experience of siblings. Participants were children, adolescents and young adults with a sibling who had undergone a BMT during childhood. Participants were recruited from a pediatric BMT clinic in Western Canada. Semi-structured, open-ended interviews that explored siblings’ memories about what it is like to be a sibling of a child who has had a BMT were conducted with each participant. Demographic data and field notes were recorded. All interviews and field notes were transcribed. The transcripts were reviewed repeatedly for significant statements in an attempt to find meaning and understanding through themes. The data analysis revealed the essence of siblings’ lived experience of transitioning through the BMT trajectory as an interruption in family life. Four themes communicated the essence of siblings’ lived experience: (1) life goes on, (2) feeling more or less a part of a family, (3) faith in God that things will be okay, and (4) feelings around families. Differences between donor and non-donor siblings are highlighted. Siblings’ recommendations for health care professionals are also provided. Results from this study will help health professionals better anticipate the diverse and shifting needs and demands of siblings of pediatric BMT patients. Recommendations for future research and innovations in nursing interventions are provided. / October 2005

Prolonged periods of non-weightbearing activity result in a significant loss of bone mass which increases the risk of fracture with the initiation of mechanical loading. The loss of bone mass is partially driven by declines in bone formation yet the mechanisms responsible for this decline are unclear. To investigate the limitations of osteoblasts during disuse, marrow ablation was superimposed on hindlimb unloaded mice. Marrow ablation is a useful model to study osteoblast functionality as new cancellous bone is rapidly formed throughout the marrow of a long bone while hindlimb unloading is the most common method used to produce skeletal unloading. The specific hypotheses of this study were aimed at determining if changes in osteoblast functionality, differentiation, and/or proliferation were compromised in non-weightbearing bone in response to a bone formation stimulus. Additionally, the influence of having compromised osteoblast functionality at the time of stimulation was assessed in non-weightbearing bones. Key outcome measures used to address these hypotheses included static and dynamic cancellous bone histomorphometry, bone densitometry, and real-time polymerase chain reaction (PCR) analyses of gene expression. The results document similar ablation-induced increases of cancellous bone in both weightbearing and unloaded animals. Similarly, there was no influence of load on ablation-induced increases in cancellous bone forming surface or mineral apposition rate. Unloading did significantly attenuate the ablation-induced increase in bone formation rate, due to reduced levels of total surface mineralization. When osteoblast functionality was compromised prior to marrow ablation, bone formation rate increases were also attenuated in ablated animals due to reduced mineralization. Additionally, increases in forming surface were attenuated as compared to unloaded animals having normal osteoblast function at the time of ablation. Collectively, these data identify mineralization as the limiting step in new bone formation during periods of disuse. The caveat, however, is that when bone formation is stimulated after a period of unloading sufficient to compromise osteoblast functionality, increases in osteoblast recruitment to the bone surface are compromised.

Thesis (M. Med. Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 61-64).

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Umbilical cord blood (CB) has been used as a source of haemopoietic stem cells in both related and unrelated bone marrow transplantation and in both settings there appears to be a reduced incidence of graft-versus-host disease (GVHD) when compared to bone marrow transplantation. The aim of this study was to perform a phenotypic and cellular analysis of both cord and adult mononuclear cells <I>in vitro</I> in order to identify any immunological characteristic that could account for the apparent reduced incidence of GVHD observed, <I>in vivo</I>. For this, the cell surface phenotype, allogeneic cellular responses, cytokine secretion and expression of co-stimulatory molecule CD40L was studied. The phenotypic analysis was carried out by determining the proportion of cells expressing the CD4, CD8, CD16, CD19, CD45RA and CD45RO markers using 3 colour flow cytometric analysis. The results showed that in cord blood mononuclear cells, there was an increased number of cells expressing CD19⁺ whereas the number of cells expressing CD8⁺ was decreased compared to adult blood mononuclear cells (ABMNCs). In contrast the number of cells expressing CD4⁺ and CD16⁺ was similar in both cord blood mononuclear cells (CBMNCs) and ABMNCs. Further phenotypic analysis confirmed that cord blood contained primarily 'unprimed' T cells expressing CD45RA, while adult peripheral blood lymphocytes express mainly the CD45R 'memory' phenotype. The primary and secondary allogeneic responses of cord and adult mononuclear cells were assessed using the standard mixed lymphocyte reaction (MLR) and the primed lymphocyte test (PLT), respectively. These results showed that there was no significant difference in primary MLR responses of CBMNCs and ABMNCs. In contrast, CBMNCs had a decreased ability to mount a secondary proliferative response compared to ABMNCs. However this impaired ability to respond could be overcome by the addition of exogenous IL-2 to the cultures. The secretion of cytokines such as IL-2, IL-4, γIFN and TNF-α and the expression of CD40L on PMA- and ionomycin-activated CBMNCs and ABMNCs was also analysed by 3 colour flow cytometry. These results showed that upon activation CBMNCs produced reduced levels of cytokines and had reduced expression of CD40L. It is likely that the reduced cytokine production and CD40L expression observed is due to the predominance of CD45RA⁺ cells in CB compared to AB. In summary, this study has shown that CB and AB have different phenotypic and functional characteristics in vitro which may well explain the reduced incidence of GVHD observed in cord blood transplantation.

Bone marrow transplantation (BMT) is the treatment of choice for many malignancies and other childhood disorders. Acknowledging that the entire family is affected when a child undergoes a BMT, increasing research attention has been given to understanding this experience from the perspectives of recipients, parents and the family as a whole. Yet, minimal attention has been directed at understanding the experience of healthy siblings as they transition through the BMT experience. Before intervention studies can be undertaken that will help healthy siblings transition through the BMT experience, knowledge about the impact of the experience on siblings is needed. Accordingly, a qualitative study guided by the philosophy of hermeneutic phenomenology was conducted to elicit detailed descriptions of the lived experience of siblings. Participants were children, adolescents and young adults with a sibling who had undergone a BMT during childhood. Participants were recruited from a pediatric BMT clinic in Western Canada. Semi-structured, open-ended interviews that explored siblings’ memories about what it is like to be a sibling of a child who has had a BMT were conducted with each participant. Demographic data and field notes were recorded. All interviews and field notes were transcribed. The transcripts were reviewed repeatedly for significant statements in an attempt to find meaning and understanding through themes. The data analysis revealed the essence of siblings’ lived experience of transitioning through the BMT trajectory as an interruption in family life. Four themes communicated the essence of siblings’ lived experience: (1) life goes on, (2) feeling more or less a part of a family, (3) faith in God that things will be okay, and (4) feelings around families. Differences between donor and non-donor siblings are highlighted. Siblings’ recommendations for health care professionals are also provided. Results from this study will help health professionals better anticipate the diverse and shifting needs and demands of siblings of pediatric BMT patients. Recommendations for future research and innovations in nursing interventions are provided.

The aim of this project was to develop an in vitro functional assay for the prediction of allograft rejection following renal transplantation. This assay was also used to study acute GVHD following identical sibling bone marrow transplantation. Lymphocyte cytokine profiles were measured by ELISA (protein secretion) and flow cytometry (cytokine expression) following mitogen stimulation and MLR. In normal individuals, considerable inter-individual variations were found in both protein secretion (IL-2, IL- 4, IL-10 and IFN-γ) and cytokine expression (IL-2 and IFN-γ). Strong relationships were found between IL-2 protein and expression, IL-2 and IL-10 protein, and IL-10 and IFN-γ protein secretion. Analysis of cytokine gene polymorphisms showed no correlation between IFN-y protein secretion, frequency or gene polymorphism. Pre-transplant MLRs were set up between renal transplant patient/donors pairs and cytokine protein secretion (IL-2, IL-4, IL-6, IL-10 and IFN-γ) measured by ELISA. Analysis was performed to ascertain predictive factors of allograft rejection. Inter-individual variations were found for all cytokine profiles. Significant correlations were found between individual cytokine protein profiles including IL-10 and IFN-γ. In addition, a correlation was found between HLA-DR mismatching and both IL-10 and IFN-γ protein secreted in the MLR. Primary univariate analysis revealed that HLA and HLA-DR mismatching, female donor sex, MLR-stimulated IL-10, MLR-stimulated IFN-γ and spontaneous IL-4 secretion were associated with an increased risk of rejection. Multivariate analysis showed the strongest correlations for predicting risk of rejection to be female donor sex, HLA mismatching and MLR-stimulated IL-l 0 secretion. A combination of high HLA mismatching and high IL-l 0 secretion in MLR gave the highest risk of rejection (RR=25.5). Finally, cytokine secretion decreased when measured post-transplant. Prediction of graft survival could not be analysed due to the low number (n=6) of patients that suffered graft failure in the group. Cytokine protein secretion (IL-2, IL-4, IL-10 and IFN-γ) in MLR was also studied for prediction of GVHD after bone marrow transplantation. There was a very low MLR response by all BMT pairs, therefore analysis could not be performed.

Bone marrow transplantation (BMT) is the treatment of choice for many malignancies and other childhood disorders. Acknowledging that the entire family is affected when a child undergoes a BMT, increasing research attention has been given to understanding this experience from the perspectives of recipients, parents and the family as a whole. Yet, minimal attention has been directed at understanding the experience of healthy siblings as they transition through the BMT experience. Before intervention studies can be undertaken that will help healthy siblings transition through the BMT experience, knowledge about the impact of the experience on siblings is needed. Accordingly, a qualitative study guided by the philosophy of hermeneutic phenomenology was conducted to elicit detailed descriptions of the lived experience of siblings. Participants were children, adolescents and young adults with a sibling who had undergone a BMT during childhood. Participants were recruited from a pediatric BMT clinic in Western Canada. Semi-structured, open-ended interviews that explored siblings’ memories about what it is like to be a sibling of a child who has had a BMT were conducted with each participant. Demographic data and field notes were recorded. All interviews and field notes were transcribed. The transcripts were reviewed repeatedly for significant statements in an attempt to find meaning and understanding through themes. The data analysis revealed the essence of siblings’ lived experience of transitioning through the BMT trajectory as an interruption in family life. Four themes communicated the essence of siblings’ lived experience: (1) life goes on, (2) feeling more or less a part of a family, (3) faith in God that things will be okay, and (4) feelings around families. Differences between donor and non-donor siblings are highlighted. Siblings’ recommendations for health care professionals are also provided. Results from this study will help health professionals better anticipate the diverse and shifting needs and demands of siblings of pediatric BMT patients. Recommendations for future research and innovations in nursing interventions are provided.