This lecture focuses on the activation and differentiation of CD8+ T cells into effector cells, which play a crucial role in eliminating infected cells. It covers the mechanisms of action, including the release of cytotoxic granules and induction of apoptosis, as well as the role of CD4+ T cells in immune responses. The lecture also discusses the contraction phase of the T cell response, the formation of memory T cells, and how pathogens evade immune responses through various strategies.