CTLA4 and tuberculosis: Through Boolean analysis of BTLA, CTLA-4, and PD-1 expression on Mtb-specific CD4 T cells, we identified three distinct BTLA-expressing subsets that are significantly lower in HIV-infected active TB patients, compared with HIV-uninfected TB patients: BTLA+CTLA-4+PD-1+, BTLA+CTLA-4+PD-1−, and BTLA+CTLA-4−PD-1− cells.