NORMAL DEVELOPMENT AND FUNCTION OF NATURAL-KILLER-CELLS IN CD3-EPSILON(DELTA-5 DELTA-5) MUTANT MICE/

The CD3 epsilon polypeptide contributes to the cell surface display as well as to the signal transduction properties of the T-cell antigen r eceptor complex. Intriguingly, the distribution of CD3 epsilon is not restricted to T cells, since activated mouse, human, and avian natural killer (NK) cells do express intracytoplasmic CD3 epsilon polypeptide s. CD3 epsilon is also present in the cytoplasm of fetal thymic T/NK b ipotential progenitor cells, suggesting that it constitutes a componen t of the NK differentiation program. We report here that the genetic d isruption of CD3 epsilon exon 5 alters neither NK cell development nor in vitro and in vivo NK functions, although it profoundly blocked T-c ell development. These results support the notion that CD3 epsilon is dispensable for mouse NK cell ontogeny and function and further sugges t that the common NK/T-cell progenitor cell utilizes CD3 epsilon as a mandatory component only when differentiating toward the T-cell lineag e.