Pokeweed mitogen induced synthesis of human IgG and IgM in vitro. Technical aspects and the role of adherent cells.

The Pokeweed mitogen (PWM)-inducing in vitro synthesis of human IgG and IgM was determined by enzyme immunoassay (EIA) in culture supernatants of PWM-stimulated peripheral blood lymphocytes (PBL) from 83 healthy donors ranging from 24-46 years. Seventy five per cent were characterized as normal responders (200-2000 ng/ml IgG and IgM), 10% classified as high responders (2000-3000 ng/ml), and another 10% had a very high response (more than 5000 ng/ml of both IgG and IgM). One of 83 donors was shown to be a PWM non-responder. In 83 unstimulated cultures from the same donors 660 +/- 75 ng/ml IgG and 60 +/- 10 ng/ml IgM were measured after 8 days of incubation. Ten donors exhibited similar dose dependence of PWM-induced Ig synthesis but differed in time kinetics (optimum between 8 and 12 days of culture). Regression analysis of IgG and IgM production in 83 PWM-stimulated lymphocyte cultures from different healthy donors showed a correlation coefficient of r = 0.627. Intracellular Ig in PWM-stimulated cells was quantified by EIA technique after cell lysis in time kinetic experiments. Reproducibility and accuracy of the test system are described in detail. An excess of monocytes of more than 20% in the culture caused an inhibition of the Ig synthesis (calculated on constant numbers of B cells). Monocytes were further immobilized in FCS-coated culture plates and pulsed with PWM for 2 h. Adding unstimulated, nonadherent cells to the plates after removing the mitogen resulted in an Ig production comparable to that with the classical method.