Cytotoxic t-cell subpopulations are specialized to combat pathogens, whereas t-cell subpopulations are specialized to combat pathogens:

Cytotoxic t-cell subpopulations are specialized to combat intracellular pathogens, whereas helper t-cell subpopulations are specialized to combat extracellular pathogens.

Cytotoxic t-cell  are CD8+ cells. Cytotoxic t-cell uses granzymes to kill intracellular bacteria, that lives in the cytosol such as viruses. They identify the pathogen forgein peptids that are bounded to MHC-I on the cell surface.

cd4+ T helper (Th) cells include Th1, Th2, and Th17 cells. They contribute to aliergic reactions and fighting extracellular  parasites.