T-CELL HYBRIDOMA CO-EXPRESSING FC-RECEPTORS FOR DIFFERENT ISOTYPES .1. RECIPROCAL REGULATION OF FC-ALPHA-R AND FC-GAMMA-R EXPRESSION BY IGA AND INTERFERON

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  • 1 January 1983
    • journal article
    • research article
    • Vol. 48  (3) , 551-559
Abstract
To clarify the co-expression phenomenon of T cell Fc receptors (FcR) specific for different isotypes on the clonal level, a murine hybridoma clone T2D4 was studied. T2D4 cells originally reported to bear FcR for IgG (Fc.gamma.R) and to release a Fc.gamma.R-related T cell factor binding to IgG (Ig binding factor; IBF) proved to also have the receptor for IgA. The binding of IgA was detected by rosette formation with trinitrophenylated ox red blood cells (TNP-ORBC) after preincubation of T2D4 cells with MOPC 315 IgA having anti-TNP activity, or directly with TNP-ORBC sensitized with MOPC 315 IgA. While the binding of MOPC 315 IgA was competed for by IgA but not by IgG2A nor IgG2B, IgA failed to inhibit the rosette formation of the cells with ORBC sensitized with rabbit IgG antibody (EAox.gamma.), proving that T2D4 cells express FcR specific for IgA (Fc.alpha.R) in addition to Fc.gamma.R. Co-expression of both receptors on the same cell surface was demonstrated by a double rosette technique using TNP-quail red blood cells (TNP-QRBC) and EAox.gamma.. FC.alpha.R activity of the cells was completely abrogated by 15 min incubation with 0.1 mg/ml trypsin; Fc.gamma.R was resistant even to 1 mg/ml trypsin. The expression of Fc.alpha.R was augmented (up-regulation) by IgA at the concentration above 300 .mu.g/ml and inhibited (down-regulation) by 1000 u/ml of murine .beta.-interferon (.beta.-IFN). The expression of Fc.gamma.R was down-regulated by IgA and up-regulated by .alpha.-IFN. Fc.gamma.R and Fc.alpha.R are co-expressed and reciprocally regulated on these cell lines. The possible co-production of IBF and the Fc.alpha.R-related binding factor specific for IgA is discussed.