Intracellular growth and phagocytosis of Blastomyces dermatitidis by monocyte-derived macrophages from previously infected and normal subjects.

Blastomyces dermatitidis evokes responses of human cellular immunity typical of other intracellular fungal pathogens. Differences in growth rates of intracellular Blastomyces yeast and the differences in amounts of yeast phagocytized by macrophages were determined for macrophages derived from peripheral blood monocytes from 11 persons with treated blastomycosis and 11 normal, healthy persons. Cellular immunity was examined by lymphocyte uptake of [3H]thymidine in response to a specific antigen of Blastomyces yeast. Yeast were more readily phagocytized by macrophages from the previously treated donors when compared with those from the normal donors; the yeast were confirmed to be intracellular by transmission electron microscopy. Likewise, a decrease in growth rates of yeast was demonstrable in cultures of macrophages from previously treated donors as compared with normal donors. This greater efficiency of phagocytosis and growth inhibition of B. dermatitidis reflects another mechanism of human cellular immunity to this fungal infection.