PDCD1 and tuberculosis: Intriguingly, we observed that the frequency of memory CD4+ PD-1+ T cells was lower (significantly for CM and TM subsets) in the HLTBI+ group compared to either the non-co-infect group (CM p < 0.0001, TM p < 0.0001) or that with active TB (CM p < 0.0001, TM p < 0.0001), and these levels were found to be comparable to those in the HIV-negative groups.