Poly(I - C) enhanced the susceptibility of CB-17 (BALB/c) mice to acute systemic candidiasis. Poly(I . C), supernatants from poly(I - C)-treated macrophages, or alpha and beta interferons suppressed macrophage candidacidal activity in vitro. Thus, poly(I . C)-induced interferons may enhance the susceptibility of CB-17 mice to candidiasis by suppressing macrophage candidacidal activity in an autocrine fashion.