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Infect. Immun., Aug 1995, 3117-3124, Vol 63, No. 8
M Fallman, K Andersson, S Hakansson, KE Magnusson, O Stendahl and H Wolf-Watz
Nonopsonized as well as immunoglobulin-G (IgG)-opsonized Yersinia
pseudotuberculosis resists phagocytic uptake by the macrophage-like cell
line J774 by a mechanism involving the plasmid-encoded proteins Yops. The
tyrosine phosphatase YopH was of great importance for the antiphagocytic
effect of the bacteria. YopH-negative mutants did not induce
antiphagocytosis; instead, they were readily ingested, almost to the same
extent as that of the translocation mutants YopB and YopD and the
plasmid-cured strain. The bacterial determinant invasin was demonstrated to
mediate phagocytosis of nonopsonized bacteria by these cells. In addition
to inhibiting uptake of itself, Y. pseudotuberculosis also interfered with
the phagocytic uptake of other types of prey: J774 cells that had been
exposed to virulent Y. pseudotuberculosis exhibited a reduced capacity to
ingest IgG-opsonized yeast particles. This effect was impaired when the
bacterium-phagocyte interaction occurred in the presence of gentamicin,
indicating a requirement for in situ bacterial protein synthesis. The
Yersinia- mediated antiphagocytic effect on J774 cells was reversible:
after 18 h in the presence of gentamicin, the phagocytic capacity of
Yersinia- exposed J774 cells was completely restored. Inhibition of the
uptake of IgG-opsonized yeast particles was dependent on the Yops in a
manner similar to that seen for blockage of Yersinia phagocytosis. This
similarity suggests that the pathogen affected a general phagocytic
mechanism. Despite a marked reduction in the capacity to ingest IgG-
opsonized yeast particles, no effect was observed on the binding of the
prey. Taken together, these results demonstrate that Yop-mediated
antiphagocytosis by Y. pseudotuberculosis affects regulatory functions
downstream of the phagocytic receptor and thereby extends to other types of
phagocytosis.
Copyright © 1995, American Society for Microbiology
Yersinia pseudotuberculosis inhibits Fc receptor-mediated phagocytosis in J774 cells
Department of Medical Microbiology, Linkoping University, Sweden.
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