part_of signaling pathway in the adaptive immune response T cell receptor signaling pathway 2010-10-27T03:28:43Z PW:0000821 T cell receptor (TCR) signaling in developing thymocytes is important for the establishment of CD4 and CD8 lineages. Mature T cells express either CD4 or CD8 co-receptors which are essential for the interaction with peptide-bound class II or class I MHC complexes to elicit CD4 T helper (Th) or CD8 cytotoxic T lymphocyte responses, respectively. In either case, T cell-initiated signaling activates the expression of genes whose products mediate these responses. TCR signaling TCR signaling pathway pathway vpetri cell-mediated immunity pathway