Functional expression of IgA receptor FcαRI on human platelets

Fc alpha RI (CD89) is a human IgA FcR expressed on cells of myeloid lineage such as neutrophils, monocytes, tissue macrophages, eosinophils, and subpopulations of dendritic cells. Fc alpha RI mediates cell activation through Src family kinases and downstream tyrosine-based phosphorylation pathways. However, the role of IgA and the expression and role of its cognate receptor Fc alpha RI (CD89) in platelet activation are undefined. In the current study, we demonstrate that human platelets express Fc alpha RI mRNAs and proteins. Furthermore, we show that the platelet Fc alpha RI is associated with the FcR gamma-chain, and cross-linking of Fc alpha RI leads to Syk phosphorylation. Clustering of Fc alpha RI induces pre-mRNA splicing and protein production of tissue factor and IL-1 beta, suggesting novel roles for human platelet Fc alpha RI and serum IgA in thrombosis and inflammation. J. Leukoc. Biol. 84: 1492-1500; 2008.