Final answer:
The interaction of a T-cell receptor with peptide-MHC complexes and co-stimulatory signals results in T cell activation, which initiates clonal proliferation and differentiation into effector and memory cells.
Step-by-step explanation:
When a T-cell receptor (TCR) interacts with peptide-MHC complexes in the presence of co-stimulatory signals, the T cell will undergo activation. This process involves a cascade of events leading to T cell proliferation and differentiation. Specifically, activation and differentiation of cytotoxic T cells involve the recognition of an antigen presented with MHC I and interaction of CD8. The production of cytokines by the antigen-presenting cell (APC) and the cytotoxic T cell promote clonal proliferation and differentiation. Activated cytotoxic T cells can differentiate into effector cells that target pathogens or memory cells ready for subsequent exposures. Similarly, helper T cells are activated by APCs presenting processed foreign epitopes in association with MHC II, and they require both nonself epitope recognition and self-antigen recognition for activation. Once activated, the helper T cell proliferates and differentiates into subtypes.