Abstract
In this study, we investigated the effect of concanavalin-A (Con-A) on the activation of phagocytosis and killing of Candida albicans by peritoneal macrophages from suckling and adult mice. Pretreatment of adult mice with Con-A dose-dependently increased the percentage of macrophages phagocytosing C. albicans in vitro from 3.8 ± 0.9 to 24.2 ± 2.4 in the absence of serum opsonins. Addition of mannan (50 μg) and mannose (50 mM) to the incubation medium reduced phagocytosis from 21.5 ± 1.3 to 4.7 ± 1.9, suggesting that treatment with Con-A increased phagocytosis mediated by mannose receptors. Killing of C. albicans was also increased by increasing the dose of Con-A. Pretreatment of suckling mice with Con-A increased the macrophages' phagocytic and candidacidal activities by an amount similar to that observed in adult mice. Furthermore, suckling mice pretreated with Con-A survived an intraperitoneal inoculum of 5 × 107 C. albicans, whereas all control mice died within 24-48 h of infection. This suggested that increased phagocytosis and killing of C. albicans stimulated by the action of Con-A conferred early protection upon suckling mice experimentally infected with C. albicans.