CHARACTERIZATION OF FC-EPSILON-RI EXPRESSING HUMAN MONOCYTIC CELL-LINES .1. THE ROLE OF CD45 ON SIGNAL-TRANSDUCTION IN PRIMARY MONOCYTES AND CELL-LINES

Background: Recently, the high affinity receptor far IgE (Fc epsilon R I), which plays a major role in allergies, has been identified on a nu mber of different antigen-presenting cell types, including human monoc ytes from atopic and nonatopic donors. In this report human monocytic cell lines were used to test for the expression of Fc epsilon RI, reas oning that a monocytic cell line expressing Fc epsilon RI constitutive ly would be a useful tool for large scale studies on the regulation of IgE binding and signal transduction. Methods: Reverse transduction po lymerase chain reaction was applied to identify Fc epsilon RI alpha-ch ain message, flow cytometry to detect Fc epsilon RI surface expression and signal transduction on the cell lines generated by transfection. Results: We report the establishment of monocytic cell lines constitut ively expressing Fc epsilon RI (THP1-alpha 01 to THP1-alpha 40) genera ted by transfection of the cell line THP1 with a plasmid encoding the Fc epsilon RI alpha-chain only. Fc epsilon RI on the THP1-alpha lines specifically binds IgE and is functional with regard to ligand binding and signal transduction. Comparative studies between the transfectant s and primary human monocytes from nonatopic donors demonstrated the r egulatory role of the tyrosine phosphatase CD45 on Fc epsilon RI-media ted cell activation. Conclusions: Monocytic cell lines carry Fc epsilo n RI alpha-chain RNA and enhancement by transfection results in surfac e Fc epsilon RI expression on THP1. Triggering the receptor on the THP 1-alpha lines or on human monocytes, which express native Fc epsilon R I, elicits a rapid and transient calcium mobilization, prevented by co -cross-linking of Fc epsilon RI and CD45.