Influence of antimannan IgA on antimannan IgG mediated complement activation and phagocytosis of Candida albicans

• Main Author: Peters, Adam A.
• Language: EN
• Published: California State University, Long Beach 2016
• Subjects: Biology|Microbiology|Immunology
• Online Access: http://pqdtopen.proquest.com/#viewpdf?dispub=10195880

<p> <i>Candida albicans</i> is an opportunistic yeast pathogen and can cause life-threatening systemic candidiasis. The cell surface of <i>C. albicans</i> is enriched with mannan that is resistant to complement activation in the absence of antimannan antibodies. To better appreciate antimannan antibody functions in human immunity, our laboratory constructed the human recombinant antimannan Fc-free fragment M1 Fab. M1 Fab was subsequently converted to full-length human recombinant antimannan antibodies: M1g1 (IgG1), M1a1 (IgA1), M1a2 (IgA2). Each retains the identical M1 Fab binding region but differ in the isotype. Previously, our laboratory has established that M1 Fab can increase C3b deposition to <i>C. albicans </i> via the alternative pathway and that M1g1 activates the alternative and classical pathways of complement and increases phagocytosis of <i> C. albicans</i> by murine macrophages. The purpose of this study was to assess the influence of M1a1 and M1a2 on M1g1 mediated complement activation and phagocytosis of <i>C. albicans.</i> M1a1 or M1a2 was found unable to promote C3b-deposition to <i>C. albicans</i> as determined by flow cytometry and immunofluorescence microscopy. The formation of the alternative pathway convertase on <i>C. albicans</i> was promoted by M1 Fab but not by M1-Fab contained within M1a1 or M1a2. Additionally, M1g1 mediated C3b deposition was inhibited by M1a1 or M1a2 in a dose-dependent manner. Finally, M1a1 or M1a2 each significantly increased phagocytosis of <i> C. albicans</i> (<i>P</i> &lt;0.001) by human neutrophils independent of serum. The presence of M1a1 or M1a2 did not inhibit M1g1-mediated phagocytosis, indicating a redundant function of IgG1 and IgA antibodies in opsonophagocytosis. Thus, human antimannan IgA subclass variants hinder complement activation while increasing neutrophil phagocytosis of <i>C. albicans.</i> These results contribute to a more complete understanding of the role of serum IgA in host immunity.</p>