Development of specific immunity in patients with pulmonary or extrapulmonary blastomycosis.

The development of specific cellular-immune mechanisms has not been reported in human blastomycosis. We have examined lymphocyte stimulation to a fungal antigen before and during antifungal therapy in 16 patients with blastomycosis. Patients with pulmonary infection only did not have increased 3H-thymidine uptake on initial testing, but all 8 had vigorous lymphocyte stimulation as an indicator of cellular immunity after at least 2 wk of therapy. Patients with extrapulmonary blastomycosis had higher counts in response to the Blastomyces antigen before therapy. These tests differentiated between those with blastomycosis after therapy was started and normal persons or those with a nonfungal infection. Because of the delayed appearance, lymphocyte stimulation does not appear helpful for diagnosis of persons with untreated pulmonary blastomycosis, but in vitro correlates of cellular immunity developed in these patients in a similar time course as with other chronic infections.