Stimulation of lymphocytes by antigen in microplate cultures; absence of an effect of transfer factor in vitro.

The best conditions for the optimum stimulation of human leucocytes by antigens, including protein purified derivative (PPD), streptokinase-streptodornase varidase (SKSD) and tetanus toxoid have been studied in microplate cultures. The leucocytes of each donor have their own characteristic response to antigen which depends on the culturing conditions such as antigen concentrations, cell concentrations and the time of measuring the rate of DNA synthesis. Thus, no conditions provide a universal optimum for antigen stimulation in vitro. Leucocyte dialysates, i.e. potential transfer factors, have been prepared from donors, who between them are strongly positive to the antigens PPD, SKSD, tetanus toxoid, diphtheria toxoid and Keyhole limpet haemocyanin. In contrast to some previous reports these leucocyte dialysates had no effect on the thymidine incorporation by leucocytes grown in the presence of these antigens. It is suggested that the selection of optimal conditions for the response to antigen may have obscured the effect of any non-specific enhancement of reactivity b lyeucocyte dialysates.