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Eosinophil-Cryptococcus neoformans interactions in vivo and in vitro
M Feldmesser1, A Casadevall, Y Kress
1Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461-1602, USA. feldmess@aecom.yu.edu
Abstract:
Eosinophils are components of inflammatory responses to a variety of pathogens. Although a variety of beneficial and harmful functions have been ascribed to these cells, their role in protection against infectious agents remains uncertain. Previous studies have reported eosinophilic pneumonia in mice infected intratracheally with Cryptococcus neoformans. We confirmed this observation and studied the inflammatory response in the lung at day 14 by light and electron microscopy. Immunostaining for glucuronoxylomannan showed isolated cryptococci inside the eosinophilic cuffs. Eosinophils were found to be in close association with C. neoformans in vivo. Cryptococci were associated with eosinophils within eosinophilic perivascular cuffs, within granulomas, and lining the alveolar space. To further investigate this phenomenon in vitro, we isolated rat peritoneal eosinophils and studied cryptococcus-eosinophil interactions in the presence and absence of anti-capsular immunoglobulin G1 (IgG1) and IgE monoclonal antibody (MAb). Eosinophils phagocytosed C. neoformans only in the presence of specific antibody. Phagocytosis was rapid, and dense rings that appeared to consist of granule contents were formed around the organisms. Mast cells were observed to occasionally phagocytose C. neoformans in vitro in the presence of IgE MAb. Our observations suggest that eosinophils may be effector cells against C. neoformans.
Insights
Eosinophils, immune cells, may fight Cryptococcus neoformans infections. Studies show eosinophils interact with and phagocytose (engulf) the fungus, especially with antibody assistance, suggesting a protective role.
Area of Science:
- Immunology
- Microbiology
- Pathology
Background:
- Eosinophils are key inflammatory cells with debated roles in pathogen defense.
- Previous research indicated eosinophilic pneumonia in Cryptococcus neoformans-infected mice.
Purpose of the Study:
- To investigate the interaction between eosinophils and Cryptococcus neoformans in vivo and in vitro.
- To determine if eosinophils can eliminate the fungus and under what conditions.
Main Methods:
- Light and electron microscopy of mouse lungs infected with C. neoformans.
- In vitro studies using rat peritoneal eosinophils and C. neoformans, with and without specific monoclonal antibodies (IgG1, IgE).
Main Results:
- Eosinophils were found in close association with C. neoformans in infected mouse lungs, within cuffs, granulomas, and alveoli.
- In vitro, eosinophils phagocytosed C. neoformans only when specific antibodies were present.
- Antibody-mediated phagocytosis by eosinophils was rapid, with granule contents forming rings around the fungi.
Conclusions:
- Eosinophils demonstrate direct interaction with and phagocytosis of C. neoformans, particularly when opsonized by antibodies.
- These findings suggest eosinophils may function as effector cells against C. neoformans infections.