What is the role of T cytotoxic cells (Tc, CD8+) in the immune response?

T cytotoxic cells, also known as CD8+ T cells, play a crucial role in the immune response by directly targeting and destroying cells that have become infected with viruses or other intracellular pathogens. These cells recognize infected cells through specific interactions between their T cell receptors and peptide fragments presented on major histocompatibility complex (MHC) class I molecules on the surface of the infected cells. Once recognized, Tc cells initiate a series of actions that lead to the apoptosis (programmed cell death) of the infected cells, effectively halting the spread of the infection.

This cytotoxic action is fundamental to the adaptive immune response, as it helps eliminate cells that are a source of viral replication and helps protect the host from further spread of the disease. The ability of T cytotoxic cells to recognize and kill infected cells is essential for controlling viral infections and is why they are key players in the immune system's defense mechanisms.

The other choices reflect different functions in the immune system: antibody production is primarily the role of B cells, T helper cells are involved in activating B cells and assisting other immune responses, and enhancing blood flow to tissues is a role associated with inflammatory responses, rather than a direct action of CD8+ T cells.