| C. albicans is one the most frequent causes of nosocomial bloodstream infections. Opsonophagocytosis plays a key role in host resistance to disseminated candidiasis. However, factors that influence opsonophagocytosis are still not well understood. The purpose of this study was to employ a complete set of anti-mannan human recombinant IgG antibody variants, M1g1, M1g2, M1g3, and M1g4 to determine the effect of subclass specificity on phagocytosis of C. albicans, mediated by anti-mannan antibody alone or anti-mannan antibody and complement. Human neutrophils were incubated with increasing amounts of each of the four IgG variants and C. albicans yeast cells and phagocytosis indexes were determined. It was found that the M1 IgG subclass variants significantly enhanced phagocytosis in a dose dependent manner (P ≤ 0.001) with M1g1 and M1g3 being the most active, followed by M1g2, and then M1g4 (P ≤ 0.001). Next, phagocytosis of C. albicans cells by human neutrophils in the presence of both antimannan antibody and complement as opsonins were examined.;No synergistic effect on phagocytosis occurred when both opsonins were present. Instead, the results showed a redundant or possibly antagonistic effect. To assess the role of complement alone in opsonophagocytosis, the M1 Fab fragment that has no Fc region was used. Significant phagocytosis of C. albicans by human neutrophils occurred when both complement and M1 Fab was present, indicating that complement opsonization promotes phagocytosis. Overall similar data were also obtained with the neutrophil-like cell line, HL-60. These observations together suggest that anti-mannan antibody or complement alone promotes opsonophagocytosis of C. albieans but their combined effect do not appear to be synergistic. |
