Role of the Fc gamma R subclasses Fc gamma RII and XXXX in the activation of @entity1 neutrophils by low and @entity7110 .

@entity1 @entity7110 @entity10685 @entity1334 @entity4071 @entity141 @entity35169
Two @entity10685 (Fc gamma R) subclasses on @entity1 neutrophils, Fc gamma RII and @entity4071 , activate different cellular functions. To examine the involvement of each receptor subtype in polymorphonuclear leukocyte activation, @entity1334 and F(ab')2 fragments of subclass-specific monoclonal antibodies ([mAbs] mAb IV.3 against Fc gamma RII and mAb 3G8 against @entity4071 , respectively) were used to block the binding of @entity7110 ( @entity7110 ) and @entity7110 ( @entity7110 ). Flow cytometry then permitted the simultaneous quantitation of antibody and ligand binding, the elicited intracellular @entity141 concentration (delta[ @entity141 ]int), initiation of the oxidative burst, and/or the @entity35169 activation in the same cell. We have previously demonstrated that subsaturating dosages of HIC bind uniformly to all the cells but elicit an "all-or-none" (i.e., dose independent) maximal delta[ @entity141 ]int in a dose-dependent subpopulation of the cells. In contrast, both the proportion of cells responding and the magnitude of the delta[ @entity141 ]int transient depend on the subsaturating dose of LIC, even though it too binds uniformly to all the cells, nonresponding as well as responding. These earlier findings have here been extended by single cell flow cytometric analysis to demonstrate that F(ab')2 @entity4071 is the major Fc gamma R involved in HIC binding (and [ @entity141 ]int mobilization), as well as in oxidative burst and @entity35169 activation. In contrast, both receptor subclasses must be available for LIC-elicited delta[ @entity141 ]int, as blockage by either of the mAb @entity1334 or F(ab')2 fragments abrogates this response, even though LIC binding to the receptors is not decreased. Furthermore, LIC elicited little oxidative burst activity and failed to activate @entity35169 but cross-linking to achieve multivalency, previously shown to induce [ @entity141 ]int and oxidative burst responses, elicited @entity35169 activity via @entity4071 . Fc gamma RII's role appears to be modulation of the small, late @entity141 influx observed at > 1 min, whereas @entity4071 modulates all the earlier larger events. Thus, simultaneous observation of receptor identity, receptor occupancy, and consequent activation parameters in the same cell by flow cytometry permits use to demonstrate that Fc gamma RII is necessary for the small signal transduction elicited by LIC; it plays a relatively small role in polymorphonuclear leukocyte stimulation by HIC. @entity4071 is the main receptor responsible for immune complex-elicited polymorphonuclear leukocyte responses; its efficacy is greatly enhanced when the receptors are cross-linked, either by preequilibrated multivalent complexes or by in situ cross-linking of bound LIC with excess antibody.
