Probable role in assembly and expression of the TCR complex as well as signal transduction upon antigen triggering. The TCR/CD3 complex of T-lymphocytes consists of either a TCR alpha/beta or TCR gamma/delta heterodimer coexpressed at the cell surface with the invariant subunits of CD3 labeled gamma, delta, epsilon, zeta, and eta. CD3-zeta forms either homodimers or heterodimers with CD3-eta. Interacts with SLA and SLA2. Interacts with DOCK2 and TRAT1. Interacts with HIV-1; this interaction up-regulates the expression of the Fas ligand (FASLG) at the cell surface. Interacts with HIV-2 Nef protein; this interaction induces down-regulation of cell surface TCR/CD3 complexes.