Cells and mediators which participate in immunoglobulin synthesis by human mononuclear cells. III. Null cells secrete a factor(s) (human immunoglobulin synthesis/secretion-facilitating factor) that can replace the null cells in the synthesis of immunoglobulin by cultured B cells.
In the accompanying communication, it was demonstrated that the null cells, the TM cells, monocytes and PWM are all obligatory participants in the synthesis and secretion of immunoglobulins by human B cells in culture. Here we demonstrate that the null cells secrete a factor, referred to as human immunoglobulin synthesis/secretion-facilitating factor (HISFF) that can replace the null cells in the cultures. HISFF is distinct from the known T cell-derived interleukins. HISFF functions in an HLA-unrestricted fashion since it can facilitate the synthesis and secretion of immunoglobulins by allogeneic B cells. The null cells cultured with TM helper cells and PWM required monocytes in the culture in order to secrete HISFF. Furthermore, B cells cultured with TM cells in medium containing HISFF, monocyte-derived factors and PWM nevertheless required monocytes in order to respond to the HISFF signal. Thus, the monocyte plays a pivotal role in the secretion of and response to HISFF. Normal levels of immunoglobulin were synthesized even when HISFF was added to the cultures of B cells, TM cells and monocytes, in the presence of PWM, as late as day 6 of the 7 day culture. We conclude that the null cells participate in immunoglobulin synthesis by the B cells by secreting a soluble mediator, HISFF, capable of replacing the null cells in the culture; and that the HISFF signal is the last signal received by the B cell before it begins to synthesize and secrete immunoglobulins.
Taylor
S
S
Department of Pathology, University of Ottawa, Ontario, Canada.
Jodouin
C A
CA
Richter
M
M
D001402:B-Lymphocytes / Q000276:immunology*; D001685:Biological Factors / Q000502:physiology*; D002478:Cells, Cultured; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis*; D008211:Lymphocyte Cooperation; D008215:Lymphocytes, Null / Q000378:metabolism* / Q000502:physiology; D009000:Monocytes / Q000502:physiology; D015398:Signal Transduction; D006377:T-Lymphocytes, Helper-Inducer / Q000502:physiology
D001685:Biological Factors; D007075:Immunoglobulin M