TCR-ASSOCIATED ZETA-FC-EPSILON-RI-GAMMA HETERODIMERS ON CD4(-)CD8(-) NK1.1(-CELLS SELECTED BY SPECIFIC CLASS-I MHC ANTIGEN() T)

The origin of autoreactive CD4(-)CD8(-) T cells is largely unknown. In TCR transgenic (Tg) mice expressing the cognate class I MHC antigen, CD4(-)CD8(-) T cells differed depending on characteristics of Tg-TCR/a ntigen interaction. Tg-TCR/CD3(lo) CD4(-)CD8(-) T cells expressing the NK1.1 marker were observed only for a Tg-TCR whose stimulation by ant igen was independent of CD8. Unlike normal T cells, which have essenti ally TCR-associated zeta homodimers, these cells had a high proportion of TCR-associated zeta-Fc epsilon Rl gamma heterodimers. They were al so characterized by an unusually high content of Fc epsilon Rl gamma m RNA and low content of mRNA encoding CD3 epsilon, CD3 gamma, CD3 delta , and zeta. Based on their phenotype and selection requirements, it is proposed that CD4(-)CD8(-) thymic precursor cells can be driven along the CD4(-)CD8(-)NK1.1(+) pathway following coreceptor-independent TCR signaling at an intrathymic stage when Fc epsilon Rl gamma and CD3 co mponents are coexpressed.