CD8A and respiratory syncytial virus infectious disease: Likewise, in respiratory syncytial virus infection but also in pulmonary infections in general, Tregs and Th17 cells have opposing features determining clinical severity (136, 177, 180, 181): Tregs promote viral clearance by recruiting CD8+ cytotoxic T cells to the lungs and limiting inefficient or excessive T cell responses (Th2, CD4+ and CD8+) (182–186).