Final answer:
Cytotoxic T cells are activated for intracellular pathogens, while helper T cells are activated for extracellular pathogens.
Step-by-step explanation:
The class of T cells that will be activated for intracellular pathogens is cytotoxic T cells. Intracellular pathogens, such as viruses, infect and replicate inside host cells. Cytotoxic T cells recognize antigens presented on the cell surface by MHC I molecules, which are expressed by infected cells. Once activated, cytotoxic T cells target and kill infected cells, along with the intracellular pathogens within.
On the other hand, the class of T cells that will be activated for extracellular pathogens is helper T cells. Extracellular pathogens, such as bacteria and parasites, are processed and presented in the binding cleft of a class II MHC molecule by antigen-presenting cells (APCs). This interaction is strengthened by the CD4 molecule, which is associated with helper T cells. Activated helper T cells play a central role in coordinating and directing immune responses against extracellular pathogens.