The limited early pulmonary CD4+ T cell response in C3HeB/FeJ mice was not due to an absence of live M. tuberculosis in lung-draining lymph nodes for T cell priming, since viable M. tuberculosis was detectable in both C57BL/6 and C3HeB/FeJ mice at 14 days after infection with HN878 (Fig. S1 g). Here, CD4 is linked to infection.