Influence of aging on murine neutrophil and macrophage function against Candida albicans

Previous work by our group showed that aged C57BL/6 mice develop an altered innate and adaptive immune response to Candida albicans and are more susceptible to systemic primary candidiasis. In this work, we used young (2-3 months old) and aged (18-20 months old) C57BL/6 mice to study in vitro the influence of aging on (1) the fungicidal activity of neutrophils and macrophages, (2) the production of cytokines by resident peritoneal macrophages in response to C. albicans, and (3) cell surface Toll-like receptor (TLR) 2 expression on resident peritoneal macrophages. Our results indicate that murine phagocytes have a fungicidal activity well preserved with aging. In vitro production of proinflammatory cytokines (IL-6, IL-1 beta, and tumor necrosis factor-alpha and chemokines (MIP-2) by purified (CD11b(+)) peritoneal macrophages in response to yeasts and hyphae of C. albicans was significantly lower in aged mice as compared with young mice. However, the production of IL-10 by macrophages, in response to C. albicans, was similar in both young and aged animals. Moreover, baseline TLR2 surface expression level was lower on aged macrophages than on control macrophages. Taken together, these data indicate that the increased susceptibility to C. albicans disseminated infections in aged mice is correlated with defects in TLR2 expression and in cytokine production, but not with an impaired fungicidal activity.