Tuesday, 12 August 2008

Candida albicans: Escaping the host's immune response

Genus: Candida
Family: Saccharomycetaceae
Order: Saccharomycetales
Class: Saccharomycetes
Subphylum: Saccharomycotina
Phylum: Ascomycota

So... the question that I would like to ask is ... If C.albicans is eluding the immune system, then isn't the immune system compromised? Does the immune system have to be compromised already for infection by C.albicans to occur? The following are quotes from a paper investigating the effect of the yeast and hyphal forms of C.albicans on differentiating monocytes in the human immune system.

"A special feature of C. albicans that is likely to play an important role in evasion of the immune response is the morphological transition from a unicellular yeast (Y) form to an elongated, multinucleate hyphal or mycelial form through the critical stage of germ tube (GT) formation. Conversion from the Y form to the GT form is strictly associated with virulence, as demonstrated by the fact that several mutants with the hypha-specific genes deleted, as well as wild-type strains unable to grow into the mycelial form, invariably have low systemic pathogenicity"

"The different modulatory effects exerted by Y and GT forms of C. albicans on differentiating monocytes may be a key phenomenon that contributes to an explanation of the intriguing paradox that distinguishes this fungus, as represented by its persistence in some body compartments as a commensal yeast or as pathogen hyphae despite the presence of vigorous cellular and humoral systemic immune responses."

"Thus, the differentiation of human monocytes into DCs appears to be tunable and exploitable by C. albicans to elude immune surveillance."

Candida albicans Yeast and Germ Tube Forms Interfere Differently with Human Monocyte Differentiation into Dendritic Cells: a Novel Dimorphism-Dependent Mechanism To Escape the Host's Immune Response
Antonella Torosantucci, Giulia Romagnoli, Paola Chiani, Annarita Stringaro, Pasqualina Crateri, Sabrina Mariotti, Raffaela Teloni, Giuseppe Arancia, Antonio Cassone, and Roberto Nisini

Infect Immun. 2004 February; 72(2): 833–843. doi: 10.1128/IAI.72.2.833-843.2004.

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