Human lymphocyte blastogenesis induced by living and dead Histoplasma capsulatum yeasts and soluble yeast autolysate.

Human peripheral blood mononuclear cells were cultured with either replicating yeast phase Histoplasma capsulatum, intact dead yeasts of soluble yeast phase autolysate antigen for induction of lymphocyte blastogenesis. H. capsulatum replicated to the same extent in cultures of lymphocytes from histoplasmin skin test-positive and negative cell donors, but stimulated far greater blastogenesis in the former. Dead H. capsulatum yeasts, which were more easily quantified, caused nearly as much specific blastogenesis as live yeasts. Blastogenesis was induced by as few as 1 dead yeast per 10,000 lymphocytes, indicating the antigenic potency of Histoplasma yeasts. Specific blastogenesis was also caused by soluble yeast autolysate. Thus, replicating H. capsulatum yeasts, dead yeasts and autolytically released soluble yeast phase antigen each stimulated specific blastogenesis of lymphocytes from persons sensitized to H. capsulatum in vivo.