CD4(+)-T-cell-mediated resistance to systemic murine candidiasis induced by a membrane fraction of Candida albicans

We induced resistance to systemic Candida albicans infection through CD4(+) -cell-mediated immunity in mice by immunization with subcutaneous injection s of live C. albicans cells emulsified in incomplete Freund adjuvant. Using the resistant mice, we tested subcellular fractions of C. albicans cells f or antigenicity. The fractions were derived from digested surface cell wall s, insoluble membranes, or soluble and insoluble cytoplasmic materials, whi ch were prepared by treatment with cell wall-digesting enzymes followed by lysis of the consequent protoplasts. Interestingly, the live-cell-immunized mice showed strong cell-mediated immune responses to the membrane fraction (C. albicans membrane antigen [CMA]). In addition, immunization with CMA i nduced resistance to systemic candidiasis, which disappeared upon administr ation of anti-CD4 monoclonal antibody. Infusion of splenocytes from the CMA -immunized mice conferred resistance on SCID mice, whereas infusion of CD4( +)-T-cell-depleted splenocytes mas unable to induce resistance, indicating the importance of CD4(+) lymphocytes for resistance. These results suggest a potential for the membrane fraction to act as an antigen conferring resis tance to systemic candidiasis in place of live cells and also as a source f or the isolation of a nem antigen.