Page 869 - Veterinary Immunology, 10th Edition

VetBooks.ir Immunity to Fungal Infections

Fungal infections are of three major types (Fig. 26.9). The first are
primary infections by fungi that affect the skin or other surfaces,

such as Microsporum or Candida species, and cause diseases such as
ringworm or thrush. The second type includes primary infections
by dimorphic fungi that mainly cause respiratory infections, for
example Histoplasma capsulatum, Blastomyces dermatitidis, and
Coccidioides immitis. The third type consists of secondary infections

by opportunistic fungi in immunodeficient animals, such as the
Mucorales (Rhizopus, Mucor, and Absidia) and Pneumocystis. The
body uses both innate and adaptive immune mechanisms to defend

itself against primary infections. Thus innate immune mechanisms
against invasive fungi such as Candida or Aspergillus species include
activation of the alternate complement pathway, resulting in
attraction of neutrophils and attempts by these neutrophils to
destroy the invading hyphae or pseudohyphae. Neutrophils are

also activated by the IL-23/IL-17 axis during fungal infections.

FIG. 26.9 The mechanisms of antifungal immunity.

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