By using multi-parameter flow cytometry to examine IL-10 expression in active pulmonary TB (PTB) and latent TB (LTB) individuals, we demonstrate that PTB is associated with expanded IL-10 expression by all CD4+ helper T cell subsets following TB antigen stimulation and that IL-10 expressing Th1 cells and aTregs exhibit the highest degree of correlation with bacterial burden and lung pathology. Here, IL10 is linked to tuberculosis.