Functional expression of IgA receptor FcRI on human platelets

Abstract: FcRI (CD89) is a human IgA FcR ex-pressed on cells of myeloid lineage such as neutro-phils, monocytes, tissue macrophages, eosinophils, and subpopulations of dendritic cells. FcRI me-diates cell activation through Src family kinases and downstream tyrosine-based phosphorylation pathways. However, the role of IgA and the expres-sion and role of its cognate receptor FcRI (CD89) in platelet activation are undefined. In the current study, we demonstrate that human platelets ex-press FcRI mRNAs and proteins. Furthermore, we show that the platelet FcRI is associated with the FcR -chain, and cross-linking of FcRI leads to Syk phosphorylation. Clustering of FcRI in-duces pre-mRNA splicing and protein production of tissue factor and IL-1, suggesting novel roles for human platelet FcRI and serum IgA in throm