Effects of the protein tyrosine phosphatase CD45 on Fc gamma RIIa signaling and neutrophil function

Objective. Neutrophil receptors for the Fc portion of IgG (Fc gamma R) trig ger immune responses following cross-linking by IgG-coated foreign particle s or immune complexes. Membrane-associated CD45, a protein tyrosine phospha tase termed leukocyte common antigen, has been shown to be essential for an tigen receptor kinase mediated signaling in lymphocytes, and we hypothesize d that CD45 may play a similar role in Fc gamma R-mediated signaling and im mune function in human neutrophils. Methods. The experimental approach was that of cell surface molecule ligati on via cross-linking with specific antibodies. Antibody dependent cellular cytotoxicity (ADCC) was assessed using a single-cell plaque assay and IL-6 production measured using ELISA, Tyrosine phosphorylation levels were asses sed with anti-phospho-tyrosine blots and F-actin polymerization by flow cyt ometry and confocal microscopy, Results. Neutrophils pretreated with anti-CD45 had a reduced ability to per form ADCC compared to untreated neutrophils, Fc gamma RIIa cross-linking re sulted in significantly increased concentrations of secreted IL-6 compared to untreated neutrophils, and IL-6 production was further enhanced by cocro ss-linking CD45 with Fc gamma RIIa, Cross-linking CD45 alone also induced I L-6 production, Fc gamma RIIa cross-linking resulted in increased protein t yrosine phosphorylation and F-actin polymerization in neutrophils. Cocross- linking CD45 with Fc gamma RIIa resulted in abrogation of Fc gamma RIIa med iated tyrosine phosphorylation and F-actin polymerization, Conclusions. These data provide evidence that CD45 can regulate or enhance the stimulation and function of human neutrophils mediated through Fc gamma R(s), In addition, CD45 ligation may play an essential role in cytokine in duction pathways that lead to inflammatory reactions in vivo. (C) 2000 Inte rnational Society for Experimental Hematology, Published by Elsevier Scienc e Inc.