IgC_TCR_delta: Constant domain of the delta chain of delta/gamma T-cell antigen receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are composed of alpha and beta, or gamma and delta, polypeptide chains with variable (V) and constant (C) regions. The majority of T cells contain alpha-beta TCRs but a small subset contain gamma-delta TCRs. Alpha-beta TCRs recognize antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma-delta TCRs recognize intact protein antigens; they recognize protein antigens directly and without antigen processing, and MHC independently of the bound peptide. Gamma-delta T cells can also be stimulated by non-peptide antigens such as small phosphate- or amine-containing compounds.