CD16-EXPRESSING CD8-ALPHA-ALPHA(-LYMPHOCYTES IN THE INTESTINAL EPITHELIUM - POSSIBLE PRECURSORS OF FC-GAMMA-R(-)CD8-ALPHA-ALPHA(+) T-CELLS() T)

T lymphocytes normally express their Ag receptors in association with the CD3 proteins, which include CD3 zeta. In CD3 zeta(eta)(null) mice thymic and peripheral T lymphocytes do not express the TCR/CD3 complex on their surface due to retention in the endoplasmic reticulum of the remaining polypeptide chains, However, intestinal intraepithelial lym phocytes (iIEL) of CD3 zeta eta(null) mice do express surface TCR, bec ause the Fc epsilon RI gamma chain replaced the CD3 zeta chain in the TCR/CD3 complex, Here we report that in a subset of CD8 alpha alpha(+) ilEL the presence of the Fc epsilon RI gamma chain could be accounted for by the surface expression of the Fc gamma RIII(CD16) complex, Bec ause in wild-type (wt) mice only CD16(+) iIEL coexpressed Fc epsilon R I gamma and CD3 zeta, we concluded that the presence of Fc epsilon RI gamma was dictated by its required participation of CD16 complex, CD8 alpha alpha(+) ilEL bearing CD16 and B220 were also detected in the in testinal mucosa of RAG-2(null) mice from 12 days after birth onward, T wo independent experimental settings were used in an attempt to demons trate that CD16(+) iIEL matured into CD16(-) T cells. First, in the RA G-2(null) mice, ilEL responded to in vivo administration of an anti-CD 3 epsilon mAb by progression to a more mature stage of development, ch aracterized by a loss of CD16 and B220, Secondly, a conversion to CD16 (-) iIEL occurred upon transfer of wt CD16(+) ilEL into RAG-2(null) mi ce, We conclude from these experiments that in both RAG-2(null) and wt mice, a precursor/progeny relationship may exists between CD16(+)B220 (+)CD8 alpha alpha(+) and CD16(-)B220(-)CD8 alpha alpha(+) iIEL.