(A) Cellular responses to Mtb purified protein derivative (PPD) in PBMCs from PPD-negative rhesus macaques (open squares, n=30), PPD-negative humans residing in the U.S. (closed circles, n=16), and humans residing in Malawi (open circles, n=20) expressed as log10 IFNγ-ELISpot spot-forming cells/million PBMCs. (B) Humoral responses to Mtb whole cell lysate (WCL) from the same groups based on log10 total Ig ELISA titer. (C-E) Mtb cellular responses plotted against Mtb humoral response. No significant correlation was identified in any of the three groups between cellular and humoral immune responses to Mtb. Bars in panels A and B represent medians. Zero values for ELISpot are plotted on the axis. Comparisons in panels A and B based on Kruskal-Wallis test with Dunn's correction for multiple comparisons. **P<0.01.