Immune L3T4+ and Lyt-2+ lymphocytes play an important role in the acquired resistance of mice to challenge with virulent Candida albieans, and release macrophage-activating cytoldnes in response to yeast cells in vitro. To determine whether antigen (Ag)-specific cytotoxic T lymphocytes are generated during fungal infection, purified L3T4+ and Lyt-2+ lymphocytes from immunized mice were cultured in the presence of syngeneic accessory cells, Candida Ag, and IL-2. Yeastinfected bone marrow macrophages and peritoneal exudate neutrophils were used as target cells in a standard SiCr release assay. Ag-specific, MHC-unrestricted lysis of infected macrophages was evident with immune Lyt-2+ cells after 5-10 days in culture. Under the same experimental conditions, the cytotoxic activity of L3T4+ cells was negligible, but its expression could be induced by the addition of anti-CD3 antibody.
Culturing immune Lyt-2+ cells for shorter periods of time (1-2 days) resulted in preferential lysis of infected neutrophils. In addition, at limiting effector cell numbers, Ag-specific MHCrestricted lymphocytes with cytotoxic activity to infected macrophages could be identified. We suggest that C. albieans infection stimulates multiple cytotoxic T-cell precursors with varying recognition stringency, wich may have an important role in antifungal resistance in vivo.