CD4 and infection: CD4+ T cells from high-pathology strains respond to Sm-p40 with strong Th1/Th17 polarization, similar to that observed in experimental infection; however, CD4+ T cells from low-pathology strains remain unresponsive.(13,14) This observation suggests that the anti-Sm-p40 CD4+ T cell response may be pivotal for the exacerbation of the strong Th1/Th17 polarized reaction that precedes and correlates with the development of severe pathology.(15)