B lymphopoiesis is regulated by cytokines, chemokines and cell surface proteins that initiate signal transduction pathways necessary for maturation to proceed. Many of these factors are expressed by cells in the surrounding bone marrow (BM) microenvironment, which also form the niches that support development. Interleukin-7 (IL-7) is an essential cytokine for progenitor B cells and is important in providing survival, proliferation and maturation signals. By growing BM B cells for extended periods of time in vitro with IL-7 it is possible to select for cells that possess the ability to grow indefinitely, and these cultures can be used to generate cell lines. Data presented herein describe the generation and characterization of IL-7-dependent B cell lines as well as their utility in investigating aspects of B cell development. As B cells mature they lose responsiveness to IL-7, yet retain IL-7 receptor expression. I demonstrate that a B cell’s ability to respond to IL-7 is controlled by the expression of suppressor of cytokine signaling (SOCS) proteins, which are regulated by a variety of signaling pathways including those initiated by IL-7. Development of progenitor B cells to mature immunoglobulin secreting B cells is mediated in part by surface proteins present on stromal cells as well as on B cells themselves. Heparan sulfate and CD19 play important roles in regulating this transition and I provide data that demonstrates how their ability to regulate Erk activation downstream of the pre-B cell receptor (pre-BCR) alters the proliferation and maturation of developing B cells.

B lymphopoiesis is regulated by cytokines, chemokines and cell surface proteins that initiate signal transduction pathways necessary for maturation to proceed. Many of these factors are expressed by cells in the surrounding bone marrow (BM) microenvironment, which also form the niches that support development. Interleukin-7 (IL-7) is an essential cytokine for progenitor B cells and is important in providing survival, proliferation and maturation signals. By growing BM B cells for extended periods of time in vitro with IL-7 it is possible to select for cells that possess the ability to grow indefinitely, and these cultures can be used to generate cell lines. Data presented herein describe the generation and characterization of IL-7-dependent B cell lines as well as their utility in investigating aspects of B cell development. As B cells mature they lose responsiveness to IL-7, yet retain IL-7 receptor expression. I demonstrate that a B cell’s ability to respond to IL-7 is controlled by the expression of suppressor of cytokine signaling (SOCS) proteins, which are regulated by a variety of signaling pathways including those initiated by IL-7. Development of progenitor B cells to mature immunoglobulin secreting B cells is mediated in part by surface proteins present on stromal cells as well as on B cells themselves. Heparan sulfate and CD19 play important roles in regulating this transition and I provide data that demonstrates how their ability to regulate Erk activation downstream of the pre-B cell receptor (pre-BCR) alters the proliferation and maturation of developing B cells.

B lymphocytes develop from pluripotent stem cells, and differentiate to plasma cells (PCs) in reaction to signals from the supportive microenvironment. Different sets of signals, which are derived from multiple sources such as soluble cytokines and cell-cell contacts, are required at different stages of development. For instance, murine B cell progenitors require the action of interleukin-7 (IL-7) in the early phase of their development in the bone marrow (BM). The necessity for IL-7 decreases as the cell matures, and this event is correlated with the appearance of CD22. The first two chapters of this thesis focus on the early stages of B cell development that take place in the BM. In chapter 1, I examine the IL-7 response and, although I do not show a specific role for CD22 in the loss of sensitivity to IL-7, my data suggest that cis interactions involving sialic acids might modulate the IL-7 response. This section is followed by the analysis of the effect of IL-21 on B cell progenitors in the BM. IL-21 is known to regulate the terminal stages of B cell differentiation. In collaboration with Dr. Danijela Konforte, I present evidence that B cell progenitors in the BM also express a functional IL-21 receptor and that stimulation of this receptor with IL-21 accelerates the maturation pace of B cells. I further demonstrate that proB cells stimulated with IL-21 and anti-CD40 can differentiate into immunoglobulin (Ig)-secreting cells, and discuss the possibility that IL-21 plays a role during inflammation for the development of B cell progenitors in peripheral lymphatic organs. Finally, in the last chapter, in collaboration with the laboratory of Dr. Gommerman, I investigate how the microenvironment can shape the development of B cells. It has been demonstrated by my collaborators that IgA+ PCs present in the gut produce iNOS and display traits commonly associated to the myeloid lineage, and in this chapter, I describe a co-culture system with BM and gut stroma to study the conditions that sustain the generation of IgA+iNOS+ cells. In particular, I show that the presence of microbial products is one of the key factors required for their development.

B lymphocytes develop from pluripotent stem cells, and differentiate to plasma cells (PCs) in reaction to signals from the supportive microenvironment. Different sets of signals, which are derived from multiple sources such as soluble cytokines and cell-cell contacts, are required at different stages of development. For instance, murine B cell progenitors require the action of interleukin-7 (IL-7) in the early phase of their development in the bone marrow (BM). The necessity for IL-7 decreases as the cell matures, and this event is correlated with the appearance of CD22. The first two chapters of this thesis focus on the early stages of B cell development that take place in the BM. In chapter 1, I examine the IL-7 response and, although I do not show a specific role for CD22 in the loss of sensitivity to IL-7, my data suggest that cis interactions involving sialic acids might modulate the IL-7 response. This section is followed by the analysis of the effect of IL-21 on B cell progenitors in the BM. IL-21 is known to regulate the terminal stages of B cell differentiation. In collaboration with Dr. Danijela Konforte, I present evidence that B cell progenitors in the BM also express a functional IL-21 receptor and that stimulation of this receptor with IL-21 accelerates the maturation pace of B cells. I further demonstrate that proB cells stimulated with IL-21 and anti-CD40 can differentiate into immunoglobulin (Ig)-secreting cells, and discuss the possibility that IL-21 plays a role during inflammation for the development of B cell progenitors in peripheral lymphatic organs. Finally, in the last chapter, in collaboration with the laboratory of Dr. Gommerman, I investigate how the microenvironment can shape the development of B cells. It has been demonstrated by my collaborators that IgA+ PCs present in the gut produce iNOS and display traits commonly associated to the myeloid lineage, and in this chapter, I describe a co-culture system with BM and gut stroma to study the conditions that sustain the generation of IgA+iNOS+ cells. In particular, I show that the presence of microbial products is one of the key factors required for their development.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 5 uppsatser.

Case Report: Diffuse Large B Cell Lymphoma (DLBCL) is an aggressive tumor of B cells that can arise almost anywhere in the body. It is the most common type of non-Hodgkin lymphoma in adults. We report a case of double hit lymphoma, a rare subtype that has an abnormal MYC and BCL2 gene translocation and occurs in about 5% of DLBCLs. A 58-year-old male with a 15-year smoking history presented with abdominal pain accompanied by weight loss of 20 lbs, night sweats, poor appetite, and fatigue. CT angiogram showed posterior mediastinal mass 3.5x5.6x12.8 cm, massive lymphadenopathy in the retroperitoneum surrounding aorta 10.5x5.2x11cm and a large left upper quadrant mesenteric mass measuring 7.2x10.2x13.6 cm. Left abdominal mass was biopsied and pathology showed DLBCL. FISH showed double hit lymphoma. Bone marrow biopsy and aspiration was negative for involvement. LV EF was 61% per ECHO. Patient underwent PET/CT, which showed extensive adenopathy in the inferior neck, chest, and abdomen, as well as a retroperitoneal mass extending into T10-11 extradural space. International Prognostic Index (IPI) for DLBCL categorized the patient as having a poor prognosis and in the high-intermediate risk group with a 4 year overall survival of 55% and 4 year progression-free survival of 53%. The PET scan results showing multiple extranodal sites was a factor in calculating his prognosis. MRI T spine with contrast showed direct invasion of T9, 10, 11, and 12. Urgent chemotherapy was started with DA-R-EPOCH. Our case demonstrates how imaging predicts the aggressiveness of DLBCL biology. The PET scan is very important in determining the extent of disease and the stage to allow for risk stratification of patients with DLBCL.

No description available.

No description available.

During a T-dependent immune response, activated B cells enter structures called germinal centers (GC) in the follicles of secondary lymphoid organs. GC B cells proliferate and undergo diversification of their Ig through somatic hypermutation and class-switch recombination. These Ig diversifications require the activity of the enzyme activation-induced deaminase (AID). Clonal selection within GCs selects GC B cells with the highest affinities for antigen to mature into plasma cells and memory B cells. GCs are underpinned by stromal cells called follicular dendritic cells (FDC). FDC functions include secretion of B cell chemokines and the retention of Ag complexes that allow GC B cells to test the affinity of their Ig. FDCs require constitutive signaling through lymphotoxin beta receptor (LTβR) from lymphotoxin alpha-beta (LTαβ) on the surface of B cells to maintain their functions. In these studies, I investigated the properties of GCs using two primary experimental models. First, I employed genetic and pharmacological ablation of LTβR signaling to investigate the expression of AID and the function of GCs in the absence of FDCs. I determined that FDCs are not required for GC formation or the expression of AID in lymph nodes, but that FDCs are crucial for affinity maturation. Second, I examined the competition between AID-/- and WT B cells in the GCs of mixed BM chimeras to investigate the role of affinity maturation during clonal selection. I found that AID increases GC B cell apoptosis, likely by inducing DNA damage, and that this is important in regulating GC size. I also found that AID-/- B cells accumulate at the centrocyte stage of the GC reaction and that this is due to a partial block in plasma cell maturation.