DIFFERENTIAL CONTRIBUTION OF THE FCR-GAMMA CHAIN TO THE SURFACE EXPRESSION OF THE T-CELL RECEPTOR AMONG T-CELLS LOCALIZED IN EPITHELIA - ANALYSIS OF FCR-GAMMA-DEFICIENT MICE

The function of the Fc receptors gamma chain (FcR gamma) for the expre ssion of the T cell receptor (TCR) complex and for T cell development, especially for T cells localized in epithelia, was investigated by an alyzing FcR gamma-deficient mice. In wildtype mice, CD8 alpha alpha(+) beta(-)TCR alpha beta(+) T cells of intestinal intraepithelial lymphoc ytes (i-IEL) utilized CD3 zeta homodimers and zeta-FcR gamma heterodim ers, whereas CD8 alpha alpha(+)beta(-)TCR gamma delta(+) i-IEL used ze ta-FcR gamma and FcR gamma homodimers in the TCR complex. On the other hand, these T cells in FcR gamma-deficient mice contained only zeta h omodimers. The surface expression of the TCR complex was reduced in CD 8 alpha alpha(+)beta(-) i-IEL and dendritic epidermal T cells (DETC) i n these mice, whereas the development of these T cells was normal. The degree of reduction appeared to depend on the expression level of FcR gamma. In contrast to these populations, TCR gamma delta(+) intraepit helial T cells in reproductive organs (r-IEL) were dramatically decrea sed, suggesting that the development of r-IEL is FcR gamma-dependent, probably due to the predominant usage of FcR gamma homodimers in the T CR complex. These results indicate that the FcR gamma chain contribute s differently to the TCR expression and to the development of T cells localized in epithelia.