Innate and adaptive immunity in Candida albicans infections and saprophytism

Underlying acquired immunity to the fungus Candida albicans is usually pres ent in adult immunocompetent individuals and is presumed to prevent mucosal colonization progressing to symptomatic infection. Exploration of immunolo gical events leading to Candida resistance or susceptibility has indicated the central role of the innate and adaptive immune systems, the relative co ntribution of which may vary depending on the site of the primary infection . Nevertheless, acquired resistance to infection results from the developme nt of Th1 responses. Cytokines produced by Th1 cells activate phagocytic ce lls to a candidacidal state. In contrast, cytokines produced by Th2 cells i nhibit Th1 development and deactivate phagocytic effector cells. Because re ciprocal influences have been recognized between innate and adaptive Th imm unity, it appears that an integrated immune response determines the life-lo ng commensalism of the fungus at the mucosal level, as well as the transiti on from mucosal saprophyte to pathogen.