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Microbial immune suppression mediated by direct engagement of inhibitory Fc receptor

Claudia Monari1, Thomas R Kozel, Francesca Paganelli

  • 1Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy.

Journal of Immunology (Baltimore, Md. : 1950)
|November 4, 2006
PubMed

Insights

Microbial glucuronoxylomannan (GXM) suppresses the immune system by activating the FcgammaRIIB receptor. Antibodies can reverse this GXM-induced immunosuppression by altering receptor engagement.

Area of Science:

  • Immunology
  • Microbiology
  • Molecular Biology

Background:

  • Microbial polysaccharides can modulate immune responses.
  • Fcgamma receptors play critical roles in immune cell signaling.
  • Immunosuppression is a key factor in various diseases.

Purpose of the Study:

  • To elucidate the mechanism by which glucuronoxylomannan (GXM) induces immunosuppression.
  • To investigate the role of FcgammaRIIB in GXM-mediated immune modulation.
  • To explore strategies for reversing GXM-induced immunosuppression.

Main Methods:

  • Investigated the interaction between GXM and FcgammaRIIB.
  • Analyzed intracellular signaling pathways, including SHIP and IkappaBalpha phosphorylation.
  • Assessed cytokine production (IL-10, TNF-alpha) using blockade and antibody addition assays.

Main Results:

  • GXM directly engages and activates the inhibitory FcgammaRIIB receptor.
  • GXM-induced FcgammaRIIB activation leads to SHIP recruitment and prevents IkappaBalpha activation, resulting in immunosuppression.
  • FcgammaRIIB blockade inhibits IL-10 production and promotes TNF-alpha secretion.
  • GXM suppresses LPS-induced TNF-alpha release via FcgammaRIIB.
  • Monoclonal antibodies (mAbs) targeting GXM reversed immunosuppression by shifting FcgammaRIIB to FcgammaRIIA engagement.

Conclusions:

  • Microbial products can directly impair immune function by stimulating inhibitory receptors like FcgammaRIIB.
  • GXM utilizes FcgammaRIIB to suppress immune responses, offering a novel immunosuppressive mechanism.
  • Specific antibodies can reverse microbial-induced immunosuppression by altering Fcgamma receptor recognition.

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