Flow cytometric assessment of human peripheral blood mononuclear cells in response to a coccidioidal antigen

The in vitro responses of peripheral blood mononuclear cells (PBMC) from healthy immune and non-immune donors were assessed by flow cytometry after incubation with the coccidioidal antigen toluene spherule lysate (TSL). After 120 h of incubation with 100 microg ml(-1) of TSL, expression of the activation markers CD69, CD25 and human leukocyte antigen-DR were all significantly increased in CD3+ lymphocytes from immune donors compared to non-immune donors (P < 0.03 for all). No differences in the surface expression of the costimulatory molecules CD28, CD152 or CD154 was seen between immune and non-immune donors after either 24 or 120 h of TSL incubation, nor were differences detected in the expression of the B7 ligands CD80 or CD86 on CD14+ monocytes. The percent of CD3+ lymphocytes expressing intracellular interferon-gamma (IFN-gamma) was significantly increased in immune compared to non-immune donors and was further increased by the addition of 10 ng ml(-1) of human recombinant interleukin (IL)-12 (P < 0.05 for both). Both CD4+ and CD8+ lymphocytes contributed to IFN-gamma production. These data indicate that coccidioidal antigen stimulation of lymphocytes from healthy immune donors leads to specific expression of activation molecules and production of intracellular IFN-gamma. Addition of IL-12 leads to a significant recruitment of cells producing IFN-gamma among immune donors.