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Human defenses against Cryptococcus neoformans: an update
1Department of Medicine, California Institute for Medical Research, Santa Clara Valley Medical Center, San Jose, USA. E.Brummer@JUNO.com
Abstract:
Cryptococcus neoformans var. neoformans is an opportunistic fungal pathogen, especially in AIDS patients, and is found world-wide. On the other hand, Cryptococcus neoformans var. gatti (CN-g) is restricted to an association with two species of Eucalyptus trees. Alveolar macrophages (AM) constitute the first line of defense to Cryptococcus neoformans and offers some resistance. The inflammatory response to Cryptococcus neoformans with an influx of neutrophils and monocytes affords a second line of defense. Secretion of proinflammatory monokines by human AM is now being defined. The inflammatory phagocytes are efficient in killing Cryptococcus neoformans and offer strong resistance. T and B cell responses to infection, a third line of defense, results in production of lymphokines (IFNg, etc.) and specific antibodies. Enhancement of lymphocyte responses by IL-12 and IL-18 to Cryptococcus neoformans infection appears to be critical. Susceptibility of AIDS patients to Cryptococcus neoformans is associated with low CD4+ T cell counts and likely reduced efficacy of the second line of defense.
Insights
Cryptococcus neoformans, a fungal pathogen, particularly affects AIDS patients. The body
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- Cryptococcus neoformans var. neoformans is a global opportunistic fungal pathogen, notably affecting individuals with Acquired Immunodeficiency Syndrome (AIDS).
- Cryptococcus neoformans var. gatti (CN-g) has a more restricted ecological niche, primarily associated with specific Eucalyptus tree species.
- Alveolar macrophages (AM) represent the initial defense against Cryptococcus neoformans, providing a degree of resistance.
Purpose of the Study:
- To define the inflammatory response and cytokine secretion by human alveolar macrophages (AM) during Cryptococcus neoformans infection.
- To elucidate the roles of different immune cell populations and cytokines in host defense against Cryptococcus neoformans.
Main Methods:
- The abstract does not specify the methods used in the study.
Main Results:
- The inflammatory response, involving neutrophils and monocytes, constitutes a second line of defense, with inflammatory phagocytes demonstrating efficient killing of Cryptococcus neoformans.
- T and B cell responses, including lymphokine (e.g., Interferon-gamma) and specific antibody production, form a third line of defense.
- Interleukin-12 (IL-12) and Interleukin-18 (IL-18) enhance lymphocyte responses, appearing critical for controlling Cryptococcus neoformans infection.
Conclusions:
- Alveolar macrophages and subsequent inflammatory cell influx are crucial for controlling Cryptococcus neoformans.
- Adaptive immune responses, particularly T and B cell functions enhanced by IL-12 and IL-18, are vital for host defense.
- AIDS patients' susceptibility is linked to low CD4+ T cell counts, compromising immune defenses against Cryptococcus neoformans.