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Infect. Immun., 02 1997, 557-563, Vol 65, No. 2
ZM Dong and JW Murphy
CD18, the beta chain of the beta 2 integrin family of adhesion molecules,
is associated with three different alpha chains (CD11a, -b, and -c) and is
expressed on the surface of all types of leukocytes. CD18-containing
molecules are up-regulated on the surface of neutrophils (polymorphonuclear
cells [PMN]) in response to chemotactic agents and are implicated in
mediating adhesion to an inflamed endothelium, which is a prerequisite to
migration of PMN into infected tissues. In a previous study, we found that
a cryptococcal culture filtrate (CneF), when injected into the bloodstream
of mice to simulate the antigenemia in cryptococcosis, inhibits PMN
accumulation at the site of an inflammatory stimulus. In the present study,
we assessed the ability of CneF and its individual components, i.e.,
glucuronoxylomannan (GXM), galactoxylomannan (GalXM), and mannoprotein
(MP), to interact with CD18 on human PMN. CneF labeled with 14C was shown
to bind to human PMN in a dose-dependent manner. Pretreatment of PMN with
anti-CD18, but not an isotype-matched control monoclonal antibody (MAb) or
anti-CD11a MAb, blocked the binding of 14C-labeled CneF to PMN. In
addition, CneF, GXM, and GalXM but not MP significantly blocked the binding
of the anti-CD18 MAb to CD18 on the surface of unactivated and formyl
methionyl leucyl phenylalanine-activated PMN as determined by indirect
immunofluorescence staining and flow cytometric analysis. In the same
experiments, the cryptococcal polysaccharides did not affect the binding of
an anti-CD11a or anti-L-selectin MAb to the surface of PMN at 4 degrees C.
The results suggest that CneF and its components GXM and GalXM bind to CD18
on human PMN. Based on our findings, we propose that CD18 is a possible
molecular target of cryptococcal polysaccharides and that binding of the
polysaccharides to CD18 has the potential to inhibit leukocyte infiltration
into inflammatory sites.
Copyright © 1997, American Society for Microbiology
Cryptococcal polysaccharides bind to CD18 on human neutrophils
Department of Microbiology and Immunology, University of Oklahoma Health Science Center, Oklahoma City 73190, USA.
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