Studies in Mice Have Shown That Resident Memory Cells (T_RM) $\alpha$

Multiple Choice

Studies in mice have shown that resident memory cells (T_RM) most often take up permanent residence in the tissue where the initial infection that produced those memory cells occurred. In this location, they are poised to respond rapidly should that infection re-occur in that same location. In contrast, central memory cells (T_CM) are primarily found in secondary lymphoid organs, where they can be activated to proliferate and differentiate into effector cells when stimulated by antigen-bearing dendritic cells following re-infection. The third subset of memory cells, effector memory cells (T_EM) , are recirculating cells that can readily enter tissues at sites of inflammation or infection and are poised to rapidly respond to re-infection. The subset of T_EM cells provides an important component of protective immunity to re-infection by the same pathogen because:

A) They are the only memory cell subset that can produce effector cytokines within a few hours of antigen re-encounter.
B) They are able to respond to S1PR1 and enter the blood circulation rapidly upon re-infection.
C) They express the integrin $\alpha$ _E $\beta$ ₇ that binds to integrin ligands expressed on epithelial cells.
D) They can protect against re-infection that occurs in a different site in the body than the primary infection.
E) They can simultaneously express cytokines associated with all three effector T cell lineages.