Figure 12. Th1 and Th17 cells impact established innate immune responses during later stages of brain abscess development.

CD3⁺CD4⁺ Th1 and Th17 cells regulate neutrophil and macrophage infiltrates during later stages of CNS parenchymal infection to expedite bacterial clearance. In addition, Th1 cells target infiltrating macrophages to regulate inflammatory mediator release, whereas Th17 cells appear to preferentially affect microglia. It remains to be determined whether these events are antigen-specific or instead result from the intense chemokine gradient generated during infection and non-specific T cell activation by staphylococcal superantigens.