If the infection becomes too great macrophages will call in Dendritic cells. These cells will take parts of the pathogen, present them on there MHC 2 markers and take them to the lymph nodes.

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Once the Dendritic cells has travelled to the lymph nodes, they search out a specific T cell. The correct T cell binds to the MHC2 marker on the dendritic cell, and undergoes replication. This is called clonal selection.

T cells replicate and differentiate into memory T ells (Tm) and T helper cells (Th).  

Tm cells remain in the lymph nodes while Th cells activate other immune cells.

Since the pathogen isn’t inside the cell, Tc cells aren't used.