CD4 and tuberculosis: HBHA has been shown to induce a cytolytic CD4+ T cell subset in persons with LTBI but not active TB, suggesting a role for HBHA in the control of M. tb infection (Aerts et al., 2019), and both HBHA-induced IFN-γ responses and anti-HBHA IgA were found to be elevated in household contacts and community controls compared to untreated TB patients in TB-endemic Addis-Ababa, Ethiopia, suggesting HBHA can confer both protective cell-mediated and humoral immune responses (Belay et al., 2016).