T cell development in mice lacking all T cell receptor ζ family members (ζ, η, and FcεRIγ)

The zeta family includes zeta, eta, and Fc epsilon RI gamma (Fc gamma). Dimers of the zeta family proteins function as signal transducing subunits of the T cell antigen receptor (TCR), the pre-TCR, and a subset of Fc receptors. In mice lacking zeta/eta chains, T cell development is impaired, yet low numbers of CD4(+) and CD8(+) T cells develop. This finding suggests either that pre-TCR and TCR complexes lacking a zeta family dimer can promote T cell maturation, or that in the absence of zeta/eta, Fc gamma serves as a subunit in TCR complexes. To elucidate the role of zeta family dimers in T cell development, we generated mice lacking expression of all of these proteins and compared their phenotype to mice lacking only zeta/eta or Fc gamma. The data reveal that surface complexes that are expressed in the absence of zeta family dimers are capable of transducing signals required for alpha/beta-T cell development. Strikingly, T cells generated in both zeta/eta(-/-) and zeta/eta(-/-)-Fc gamma(-/-) mice exhibit a memory phenotype and elaborate interferon gamma. Finally, examination of different T cell populations reveals that zeta/eta and Fc gamma have distinct expression patterns that correlate with their thymus dependency. A possible function for the differential expression of zeta family proteins may be to impart distinctive signaling properties to TCR complexes expressed on specific T cell populations.