IL17A and susceptibility to pneumonia measurement: Anti-protein antibody responses were shown to protect against invasive pneumococcal disease (23, –, 26), whereas CD4+ T-cell-based immunity, in particular that mediated by interleukin-17A (IL-17A)-producing Th17 cells, plays an important role in the prevention of pneumococcal recolonization (18, 25, 27, 28) and experimental pneumonia in mice (29).