Old age‐associated enrichment of peripheral T regulatory cells and altered redox status in pulmonary tuberculosis patients

Aging influences the susceptibility and prognosis to various infectious diseases including tuberculosis (TB). Despite the impairment of T‐cell function and immunity in older individuals, the mechanism for the higher incidence of TB in the elderly remains largely unknown. Here, we evaluated the age‐associated immune alterations, particularly in effector and Treg responses in pulmonary TB patients. We also evaluated the impact of redox status and its modulation with N‐acetyl‐cysteine (NAC) in elderly TB. Higher frequency of Treg cells and reduced IFN‐γ positive T cells were observed among older TB patients. The elevated number of Treg cells correlated tightly with bacillary load (i.e. disease severity); which declined significantly in response to successful anti‐tubercular treatment. We could rescue Myobacterium tuberculosis‐specific effector T cell (Th1) responses through various in vitro approaches, for example, Treg cell depletion and co‐culture experiments, blocking experiments using antibodies against IL‐10, TGF‐β, and programmed death‐1 (PD‐1) as well as NAC supplementation. We report old age‐associated enrichment of Treg cells and suppression of M. tuberculosis‐specific effector T (Th1) cell immune responses. Monitoring these immune imbalances in older patients may assist in immune potentiation through selectively targeting Treg cells and/or optimizing redox status by NAC supplementation. Treg cells suppress T‐effector function in older TB patients. Treg depletion, inhibition of suppressive elements (i.e. IL‐10, TGF‐β, PD‐1) using blocking antibodies as well as supplementation with N‐acetyl‐cysteine may help in restoring T‐effector response and redox status among them.