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Distinct Tyrosine Kinase Activation and Triton X-100 Insolubility upon FcγRII or FcγRIIIB Ligation in Human Polymorphonuclear Leukocytes.

Two tyrosine kinase-dependent pathways exist for activation of the respiratory burst by polymorphonuclear leukocyte (PMN) immunoglobulin G Fc receptors. Direct ligation of FcγRII activates the respiratory burst, but ligation of the glycan phosphoinositol-linked FcγRIIIB does not. Instead, this receptor and the integrin complement receptor CR3 synergize in activation of the respiratory burst (Zhou, M.-J., and Brown, E. J. (1994) J. Cell Biol. 125, 1407-1416). Here we show that direct ligation of FcγRII leads to activation and Triton X-100 insolubility of the Src family kinase Fgr, without effect on the related myeloid Src family member Hck. In contrast, adhesion of PMN via FcγRIIIB leads to activation and Triton X-100 insolubility of Hck but not Fgr. The exclusive association of FcγRIIIB with Hck activation and Triton insolubility is not solely a result of its glycan phosphoinositol anchor, since decay accelerating factor (CD55), another prominent glycan phosphoinositol-anchored PMN protein, is associated with Fgr insolubility to a greater extent than Hck. Ligation of decay accelerating factor, with or without coligation of CR3, does not activate the PMN respiratory burst. Coligation of FcγRIIIB with FcγRII overcomes the pertussis toxin inhibition of H2O2 production in response to direct ligation of FcγRII. These data support the hypothesis that activation of Hck upon FcγRIIIB ligation has a role in generation of the synergistic respiratory burst.

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