CD4 and infection: Flow cytometry analyses of Th17 responses to 5CP revealed that CD4+ IL-17A+ cells were increased in nasal-associated lymphoid tissue (NALT) from 5CP-immunized mice, 5 days after the last immunization, with lower levels than those observed for GAS infection-experienced mice (Fig. 2a); however, levels of soluble IL-17A in the supernatants of homogenized NALT were comparable to those from infection-experienced mice (Fig. 2b).