What is a key difference between memory T cells and effector T cells?

Memory T cells are specifically designed to provide long-term immunity after an initial infection or vaccination. They can persist in the body for years and are crucial for a swift and effective response if the same pathogen is encountered again. This long-term presence allows for a more rapid expansion and activation of these cells upon re-exposure to the specific antigen, which increases the body's ability to eliminate the pathogen more effectively than during the first encounter.

Effector T cells, on the other hand, are short-lived cells that directly respond to current infections. They are produced during the immune response and are actively involved in eliminating pathogens at the time of infection. Once the infection is cleared, many of these effector T cells will undergo apoptosis, while some will transition into memory T cells to establish long-lasting immunity.

This distinction illustrates the role memory T cells play in sustaining immunity over time, contrasting with the immediate action of effector T cells during an active immune response.