B lymphocyte regulation of the immune system. I. In vivo biologic activity of the novel lymphokine, B cell-derived enhancing factor (BEF).
B cell-derived enhancing factor (BEF) is a lymphokine of B cell origin which was originally identified and characterized by its ability to enhance in vitro antibody responses, an effect shown to be due to the ability of BEF to reduce the activation of suppressor T cells. The present study was undertaken to determine whether BEF could also be active in modulating antibody responses in vivo. The data presented here demonstrate that BEF is biologically active in vivo, as manifested by significantly enhanced primary IgM and IgG antibody responses in mice that were either injected with BEF prepared exogenously or implanted with growing BEF-secreting cells of a B cell line. Moreover, BEF was shown to enhance subsequent development of immunologic memory in mice pretreated with BEF at the time of primary immunization; these mice then displayed enhanced secondary responses when challenged with the same antigen some weeks later. The mechanism by which BEF exerts biologic activities to positively modulate in vivo antibody responses and immunologic memory reflects the ability of BEF to modulate one or more T cell functions, as evidenced by the following findings. 1) Transient in vitro exposure to BEF of T cells, but not of B cells, endowed such cells with the capacity to adoptively transfer enhanced primary antibody responses to irradiated recipients. 2) Utilizing adoptive in vivo antibody responses, in which fractionated B cell or T cell populations were obtained from BEF-pretreated mice, revealed that one effect of BEF which results in enhanced immunologic memory is related to its activity on T cells during the priming phase of the immune response. Finally, the existence of this B cell-derived lymphokine and the demonstration of its in vivo regulatory effects on the immune system provide yet another example of the emerging biologic importance of B lymphocytes in the overall regulation of the immune system.
D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000637:transplantation; D002460:Cell Line; D005260:Female; D006133:Growth Substances / Q000008:administration & dosage / Q000494:pharmacology*; D007116:Immunization, Passive; D007156:Immunologic Memory; D015847:Interleukin-4; D008222:Lymphokines / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008811:Mice, Inbred DBA; D009368:Neoplasm Transplantation; D013154:Spleen / Q000166:cytology
D006133:Growth Substances; D008222:Lymphokines; D015847:Interleukin-4