Immune responsiveness following intratracheal inoculation with Histoplasma capsulatum yeast cells

Splenic in vitro immune responses from C57B1/6 mice have been evaluated after intratracheal (i.t.) or intravenous (i.v.) inoculation with live Histoplasma capsulatum yeast cells. Significant (P less than 0.005) numbers of cells reactive to heat killed H. capsulatum (HK-Hc) were present 1 week after i.t. inoculation with 5 X 10(5) viable yeast cells. In contrast, blastogenic responses to HK-Hc were not detected until 3 weeks after i.v. H. capsulatum inoculation. Examination of non-specific immunity, i.e. mixed lymphocyte responses to alloantigens and antibody formation to sheep erythrocytes, revealed a significant (P less than 0.005) and transient depression of these responses 1 week following i.t. H. capsulatum inoculation. The non-specific decreases associated with early (1 week) i.t. infection were not mediated by suppressor cells but were related to the number of viable yeast administered.