Immune issues in elderly with TB

The article reviews the immune changes in the elderly with particular reference to susceptibility of elderly to Tubercular infection whether new or LTBI and in the light of recent advances in the field of immune mechanisms of tubercular infection. An primary understanding of the host response to infections and M. tuberculosis (M.tb) infection in particular helps to better understand the various issues of immune response to tubercular infection in the elderly. Immune mechanisms of ageing in particular deal with the twin unique mechanisms and terms particular to aging- Immunosenescence and Inflammaging. In the elderly patient both the Innate and the Adaptive immune responses are affected at various levels. The M.tb bacteria encounters the innate immune system initially and thereafter the response is from the cells of the adaptive immune system. The M.tb bacillus which enters through the respiratory system to the bronchioles and alveolus encounters the immune system at three levels which are the Resident structural i.e. alveolar epithelium, Resident innate i.e. the alveolar and pulmonary macrophages and the Infiltrating innate i.e. the neutrophils and monocytes. Increased inflammatory changes present in the lung mucosa has been associated with changes in multiple innate molecular defence mechanisms that could influence the ability of M.tb to establish an infection, the various cellular mechanisms involved and the evasive strategies evolved by the M.tb to survive and disseminate are briefly described. The susceptibility of the elderly to develop and succumb to TB may be a direct impact of increased inflammation at every stage of infection. M.tb is a potent stimulator of multiple inflammatory responses and added to a basal inflammatory state with evasiveness of M.tb bacilli, enable it to overcome and disseminate, increasing the morbidity and mortality in the infected elderly. Hopefully a better understanding of the immune mechanisms involved will enable better preventive, diagnostic and treatment modalities.