[Human lymphocyte proliferative response and gamma-interferon production to Pneumocystis carinii antigen in vitro]

In vitro proliferative response and gamma-interferon (IFN-gamma) production to Pneumocystis carinii antigen were investigated in peripheral blood mononuclear cells (PBMC) from healthy volunteers and cord blood mononuclear cells (CBMC) from umbilical cords after delivery. Twenty three of 25 samples of PBMC had strong proliferative response, and 15 of 25 samples of PBMC produced IFN-gamma. In the samples showing strong proliferative response, CD4 lymphocytes expressed interleukin 2 receptors. None of the 3 CBMC samples had proliferative response nor production of IFN-gamma. When CD4 lymphocytes were depleted in PBMC, the proliferative response was markedly decreased and IFN-gamma production was abolished. In conclusion, the lymphocytes of healthy adults are activated and produce IFN-gamma by stimulation with P. carinii antigen, and these two response are both induced by CD4 lymphocytes.