Final answer:
Cytotoxic T cells, once activated, leave the secondary lymphoid organs and travel to the site of infection to carry out their function of killing infected cells. After controlling the infection, they reduce in number, but some persist as memory cells for a fast response upon re-exposure to the pathogen.
Step-by-step explanation:
Activation and Function of Cytotoxic T Cells
Cytotoxic T cells, also known as cytotoxic T lymphocytes or CTLs, play a crucial role in the cell-mediated part of the adaptive immune system. Their primary function is to attack and destroy cells that are infected, especially by viruses. After being activated by antigen-presenting cells (APCs) through the recognition of an antigen presented with MHC I and the interaction of the CD8 co-receptor, cytotoxic T cells proliferate and differentiate into effector cytotoxic T cells and memory cells. Effector cytotoxic T cells travel to the site of infection to perform their role, which is to identify and kill the infected host cells before the pathogens can replicate and spread. Memory cytotoxic T cells, on the other hand, remain in the body, ready to respond rapidly upon future exposures to the pathogen.
Activated cytotoxic T cells do not stay in the secondary lymphoid organs; rather, they move to the site of infection where they exert their effects. After an infection is brought under control, effector cytotoxic T cells decline in number, but a portion of them persists as memory cells, which are primed for a rapid immune response if the same pathogen is encountered again, a process known as the secondary adaptive immune response.