INVITRO IMMUNE-RESPONSE OF HUMAN PERIPHERAL LYMPHOCYTES .1. MECHANISM(S) INVOLVED IN T-CELL HELPER FUNCTIONS IN POKEWEED MITOGEN-INDUCED DIFFERENTIATION AND PROLIFERATION OF B-CELLS

Abstract

Human peripheral lymphocytes (PBL), upon stimulation with PWM [pokeweed mitogen], proliferate and differentiate to Ig[immunoglobulin]M- and IgG-producing cells. The PWM-induced Ig production in B [bone marrow-derived] cells was dependent on T [thymus-derived] cells, and cell-free supernatant (CFS) obtained from PWM-stimulated PBL or T cell-rich fraction replaced T cell helper functions. The active substance(s) in CFS were most likely derived from T cells. The kinetic studies showed that the proliferation of B cells took place in advance of the final differentiation to Ig-producing cells and that T cells or T cell product(s) had to exist at the initiation of cultures to give the maximum helper effect. The final differentiation of B cells to Ig-producing cells was not dependent on T cells. The helper effect of T cells or T cell product(s) on PWM-induced proliferation and differentiation of B cells was exerted across the MHC [major histocompatibility complex] barrier. This may make it possible to apply this experimental system to the assessment of quantitative and/or qualitative changes in human helper T cells in several immunologic diseases.