Properties of mouse CD40: the role of homotypic adhesion in the activation of B cells via CD40.
Stimulation of human B cells via CD40 is known to induce their homotypic aggregation. We show here that anti-mouse CD40 monoclonal antibodies (mAb) also induce B cells to form large, spherical, extremely stable clusters. This clustering is markedly enhanced by co-stimulation with either interleukin-4 (IL-4) or anti-immunoglobulin (Ig). The aggregation is slow in onset, and is largely (but not completely) abrogated by anti-LFA-1 mAb, but not by mAb directed against other potentially important adhesion molecules on B cells. Anti-LFA-1 mAb also partially suppressed DNA synthesis induced by anti-CD40, but not by other B cell mitogens, suggesting that clustering is an important component of B cell activation via CD40. This concept is supported by analyses of the phenotype of clustered B cells: the cells within clusters express higher levels of various activation markers, and also more of them are in cell cycle than non-clustered cells. These results therefore suggest that CD40 stimulation may either induce B cells to secrete soluble factors which act in an autocrine way to promote B cell activation, or that clustering generates cell contact-mediated signals which are important in the activation cascade.
Klaus
G G
GG
National Institute for Medical Research, London.
Holman
M
M
Hasbold
J
J
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D015815:Cell Adhesion Molecules; D016169:Lymphocyte Function-Associated Antigen-1; D004247:DNA