Incidence of potential glycosylation sites in immunoglobulin variable regions distinguishes between subsets of Burkitt's lymphoma and mucosa-associated lymphoid tissue lymphoma

Novel follicular dendritic cell molecule, 8D6, collaborates with CD44 in supporting lymphomagenesis by a Burkitt lymphoma cell line, L3055

The lymphoid follicle is a specialized microenvironment for the differentiation of antigen (Ag)–activated B cells; the major stromal cell components in lymphoid follicle are the follicular dendritic cells (FDCs). At the same time, most of the B-cell lymphomas originate from the germinal center, and the generation and blast transformation of B-cell lymphoma occurs in close association with FDCs in the early stage of tumorigenesis. To study the functional roles of FDCs in lymphomagenesis, we established an inducible tumor model. The human B-cell lymphoma cell line, L3055, formed solid tumors only when inoculated with an FDC line, HK. In addition, 2 FDC-signaling molecules (FDC-SMs), a novel protein 8D6 and 4G10/CD44, are required for tumor formation in vivo, because monoclonal antibodies (mAbs) specific to these 2 proteins inhibited lymphomagenesis completely when they were inoculated with L3055 and HK cells. However, these 2 FDC-SMs have distinct functional roles in tumor formation. FDC-SM-8D6 enhances L3055 cell proliferation, whereas FDC-SM-4G10/CD44 inhibits its apoptosis. Identification of the functional roles of these critical FDC-SMs may lead to the discovery of therapeutic drugs that suppress the survival and growth of lymphoma cells.

Incidence of novel N-glycosylation sites in the B-cell receptor of lymphomas associated with immunodeficiency

Novel N-glycosylation sites are introduced by somatic mutation into the V genes of the majority of follicular lymphomas. Sites are positively selected and rare in normal memory B cells, indicating a potential role in tumour survival in the germinal centre (GC). The incidence of c. 40% in diffuse large B-cell lymphomas (DLBCL) parallels the known heterogeneity of the disease. Immunodeficiency-related non-Hodgkin's lymphomas (NHL) include post-transplant lymphoproliferative disorders (PTLD) and acquired immunodeficiency syndrome-related NHL (AIDS-NHL). Most PTLD derive from B cells that carry mutated VH genes and that have completed the GC reaction. All AIDS-NHL carry mutated VH genes and variable features of GC or post-GC cells. To determine if N-glycosylation is a feature of immunodeficiency-related lymphomas, we analysed the VH genes of 19 PTLD and 36 AIDS-NHL. Novel sites were rare in PTLD (4/19), similar to memory B cells (P = 0.15). AIDS-NHL, including DLBCL and Burkitt's lymphomas (BL), showed heterogeneity with 16 of 36 (44%) having novel sites. The findings indicate no selection of N-glycosylation sites in PTLD, consistent with post-GC features. The variable incidence of N-glycosylation sites in AIDS-NHL mirrors that in DLBCL and sporadic BL of immunocompetent hosts, supporting the known heterogeneity of these disorders, and possibly pointing to distinct routes of tumour development.