CD4 and tuberculosis: There were no statistically significant differences in CD4 T cell proliferation following stimulation with Mtb peptides between SM+ and SM− individuals in either group; however, within the SM+ groups, TB individuals had markedly lower proliferation in response to Mtb peptides than LTBI individuals (Figure 6C), consistent with previous reports of impaired Mtb-specific CD4 T cell proliferative capacity in individuals with active TB disease (52).