EOSINOPHIL-CRYPTOCOCCUS NEOFORMANS INTERACTIONS IN-VIVO AND IN-VITRO

Eosinophils are components of inflammatory responses to a variety of p athogens. Although a variety of beneficial and harmful functions have been ascribed to these cells, their role in protection against infecti ous agents remains uncertain. Previous studies have reported eosinophi lic pneumonia in mice infected intratracheally with Cryptococcus neofo rmans. We confirmed this observation and studied the inflammatory resp onse in the lung at day 14 by light and electron microscopy. Immunosta ining for glucuronoxylomannan showed isolated cryptococci inside the e osinophilic cuffs. Eosinophils were found to be in close association w ith C. neoformans in vivo. Cryptococci were associated with eosinophil s within eosinophilic perivascular cuffs, within granulomas, and linin g the alveolar space, To further investigate this phenomenon in vitro, we isolated rat peritoneal eosinophils and studied cryptococcus-eosin ophil interactions in the presence and absence of anticapsular immunog lobulin G1 (IgG1) and IgE monoclonal antibody (MAb). Eosinophils phago cytosed C. neoformans only in the presence of specific antibody. Phago cytosis was rapid, and dense rings that appeared to consist of granule contents were formed around the organisms. Mast cells were observed t o occasionally phagocytose C. neoformans in vitro in the presence of I gE MAb. Our observations suggest that eosinophils may be effector cell s against C. neoformans.