Normal Development and Function of Natural Killer Cells in CD3εΔ 5/Δ 5Mutant Mice

The CD3ε polypeptide contributes to the cell surface display as well as to the signal transduction properties of the T-cell antigen receptor complex. Intriguingly, the distribution of CD3ε is not restricted to T cells, since activated mouse, human, and avian natural killer (NK) cells do express intracytoplasmic CD3ε polypeptides. CD3ε is also present in the cytoplasm of fetal thymic T/NK bipotential progenitor cells, suggesting that it constitutes a component of the NK differentiation program. We report here that the genetic disruption of CD3ε exon 5 alters neither NK cell development nor in vitro and in vivo NK functions, although it profoundly blocked T-cell development. These results support the notion that CD3ε is dispensable for mouse NK cell ontogeny and function and further suggest that the common NK/T-cell progenitor cell utilizes CD3ε as a mandatory component only when differentiating toward the T-cell lineage.