Phagocytosis and Acid Phosphatase Activity against Candida Albicans in Cultured Rabbit Keratocyte

ABSTRACT

It has been reported that keratocytes endocytose foreign particles both in vitro and in vivo, suggesting the active participation of keratocytes in corneal wound healing and host defense mechanism. This study was conducted to investigate the phagocytosis of keratocytes against Candida albicans[C.albicans]and the intracellular response after phagocytosis. C.albicans were fixed with glutaraldehyde and then coated with fibronectin. After exposing these C.albicans to the cultured rabbit keratocytes, the phagocytosis of keratocytes against C.albicans was evaluated by light microscope[LM]and transmission electron microscope[TEM], while the intracellular response was evaluated by changes of acid phosphatase activity. Also the study about latex beads was performed at the same time to know even if keratocytes can phagocytose foreign particles, regardless of wheather or not the particles are biodegradable. After Wright staining, phagocytosed latex beads and C.albicans were observed on LM and these were recognized to be surrounded by limiting membranes inside the cytoplasm of keratocytes on TEM. The phagocytic rates of fibronectin-coated were increased to 1.5 times , as compared with that of non-coated group. Acid phosphatase activities were higher in C.albicans-exposed groups than in control[keratocytes cultured without C.albicans or latex beads]during the culture period of 24 hours and they also increased according to culture duration and reached to the plateau after 12 hours. In comparison with non-coated group, fibronectin-coated groups showed a increasing tendency of acid phosphatase activity. These results suggest that keratocytes can phagocytose not only foreign particles but also C.albicans and that fibronectin may act as effective opsonin on phagocytosis, and that keratocytes phagocytosing C.albicans increase acid phosphatase activity to digest engulfed C.albicans when corneal stroma was wounded or inflammed.