Document 0795
 DOCN  M9440795
 TI    Opsonization and phagocytosis of Cryptococcus neoformans.
 DT    9404
 AU    Kozel TR; Department of Microbiology, School of Medicine, University of;
       Nevada, Reno 89557.
 SO    Arch Med Res. 1993 Autumn;24(3):211-8. Unique Identifier : AIDSLINE
       MED/94129171
 AB    Cryptococcus neoformans is unique among the pathogenic fungi because the
       yeast is surrounded by an antiphagocytic polysaccharide capsule. Host
       resistance to cryptococcosis is dependent on natural defense mechanisms
       that cope with this essential fungal virulence factor. Recent studies in
       several laboratories indicate that, under appropriate circumstances, the
       antiphagocytic activity of the capsule can be overcome. A reversal of
       the antiphagocytic properties of the capsule requires (i) activation of
       the alternative complement pathway by encapsulated cryptococci, leading
       to deposition of the opsonic ligand iC3b at the capsular surface, (ii)
       presence of essential cytokines which up-regulate the efficiency of
       complement-dependent phagocytosis, and (iii) availability of phagocytic
       cells whose complement receptors are capable of appropriate
       up-regulation. Deficiencies in one or more components of the
       opsonization-phagocyte-cytokine triad may account, in part, for several
       features of the pathogenesis of cryptococcosis as well as the
       susceptibility of some immunocompromised patients to cryptococcosis. It
       may be possible to overcome some deficiencies by passive immunization
       with anticapsular IgG which takes advantage of phagocyte Fc receptors
       that are constitutively competent for phagocytosis or by therapeutic use
       of cytokines that up-regulate complement-dependent phagocytosis.
 DE    Animal  Antibodies, Fungal/*IMMUNOLOGY  AIDS-Related Opportunistic
       Infections/EPIDEMIOLOGY/IMMUNOLOGY  Cell Wall/IMMUNOLOGY
       Complement/IMMUNOLOGY  Cryptococcosis/EPIDEMIOLOGY/IMMUNOLOGY
       Cryptococcus neoformans/*IMMUNOLOGY  Cytokines/IMMUNOLOGY  Host-Parasite
       Relations/IMMUNOLOGY  Human  IgG/IMMUNOLOGY  Immunity, Natural  Mice
       Opsonins/*IMMUNOLOGY  *Phagocytosis  Prevalence  Rats  Support, U.S.
       Gov't, P.H.S.  JOURNAL ARTICLE  REVIEW  REVIEW, TUTORIAL

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).