Coccidioidin Delayed Hypersensitivity: Skin Test and In Vitro Lymphocyte Reactivities

Summary Delayed skin test reactivity and in vitro antigen-induced lymphocyte proliferation were compared in three groups of subjects. Addition of coccidioidin to lymphocyte cultures led to an increased rate of isotope uptake into DNA in cells of strongly coccidioidin skin test positive subjects but not in cells of weakly coccidioidin skin test positive or of coccidioidin skin test-negative individuals. Coccidioidin-induced lymphocyte proliferation was antigen-dose dependent. There was no evidence of in vitro cross-reactivity between coccidioidin and tuberculin in lymphocyte cultures.