Immunosuppression transfer by spleen cells from young to adult mice previous to Histoplasma capsulatum infection.

The passive transfer of spleen cells from 1 month old mice into adult syngeneic mice, abrogates their resistance to histoplasmal infection. This suppressive state was detected in two cell populations, one non-adherent and another adherent with radioresistant characteristics. The transferred spleen cells were treated by different anti-sera: anti-theta, anti-adherent cells (produced in rabbits) and monoclonal anti-Thy 1.2 respectively. The irradiated and non-irradiated adult recipient mice were infected with Histoplasma yeasts utilizing the Lethal Dose50 for 1 month old mice. The infection course was determined by death percentage, the histoplasmosis murine signs and the number of the fungal colony forming units (CFU) from the infected spleens. The results of the anti-sera treatment suggest that non-adherent as well as adherent cells participate in the suppressive phenomena. A lower number of CFU was identified in infected animals which received cells treated with anti-Thy 1.2 anti-sera.