PRODUCTION OF A SOLUBLE HUMAN LYMPHOCYTE-T DERIVED FACTOR WHICH SUBSTITUTES FOR HELPER LYMPHOCYTES-T IN THE INVITRO PRODUCTION OF IMMUNOGLOBULIN

Abstract

A soluble factor(s), human T [thymus-derived] lymphocyte derived help factor (HHF), generated following pokeweed mitogen (PWM) activation of irradiated human peripheral blood T lymphocytes substituted partially for T lymphocyte helper activity in the T lymphocyte dependent PWM-stimulated synthesis of immunoglobulin [Ig] by B [bone marrow-derived] cells. The degree of help provided was proportional to the number of cultured irradiated T lymphocytes producing factor and the amount of factor added to the B cell culture. The helper effect was equally provided by HHF syngeneic and allogeneic to the B lymphocyte. Although there was little stimulation of toal protein synthesis, the synthesis and secretion of IgG, IgM and IgA were all stimulated 3- to 10-fold by this factor. The B cells required a minimum of 40-55 h exposure to the factor from the initiation of the culture for an increase in Ig synthesis on day 5 to be observed. Addition of HHF to B cells pre-incubated with PWM for different time intervals showed that a maximum helper effect was exerted when the factor was added on day 0. Addition on day 1 provided less than 20% of maximum help. The factor did not promote significant increases in either B cell or T cell cell division.