Immunosuppression in experimental cryptococcosis in rats. Induction of afferent T suppressor cells to a non-related antigen.

To demonstrate the nature of the suppressor cells elicited in rats infected with Cryptococcus neoformans and immunized with human serum albumin (HSA), spleen mononuclear (SpM) cells were fractionated through a nylon wool column. The adherent and non-adherent populations were collected and transferred to syngeneic rats. In all cases, the non-adherent or T-enriched cells adoptively transferred suppression to HSA, however, the suppressive effects of the non-adherent cells were never as great as those of the unpassed population of SpM cells. The fractions adherent to nylon wool also diminished the delayed-type hypersensitivity response to HSA although this was not significant, but glass-adherent cells did exhibit significant suppressor activity. Immunized, non-infected rats were used as donor controls. Furthermore, we showed that the T-enriched-cells are sensitive to treatment with low doses of cyclophosphamide and that they bind HSA. These data indicate that immune suppression of the induction of the delayed-type hypersensitivity response to HSA in cryptococcosis can occur as a result of infection with C. neoformans, and that at least one mechanism involved is the induction of adherent and non-adherent suppressor cells. Characterization of the non-adherent cells indicates that they are Ts1 cells.