Phenotypic characterization of Natural Killer Cells in Post Tuberculosis Pulmonary Sequelae

<bold>Rationale:</bold> Natural killer (NK) cells, key effector cells of the innate immune system, play an important role in the clearance and control of Mycobacterium tuberculosis. These cells produce high levels of proinflammatory cytokines in response to pathogens and have the capability to induce apoptosis in target cells via the release of perforin and granzymes. In view of the remarkable cytotoxic activity of NK cells, the aim of this study is to phenotypically characterise circulating NK cells in patients diagnosed with post tuberculosis sequelae. <bold>Methods:</bold> Patients having chronic anatomic and symptomatic sequelae arising from previously treated and microbiologically cured pulmonary tuberculosis (TB) (PTS, n=9), patients who recovered from pulmonary TB without having any anatomic or symptomatic sequelae (PTWS, n=10) and healthy participants (C, n=15) were recruited in this study. Flow Cytometry was performed on peripheral blood mononuclear cells to identify circulatory NK cells with phenotype CD3-CD56+Granzyme+/Perforin+. <bold>Results:</bold> The percentage of NK cells (CD3-CD56+) was significantly lower in post TB with sequelae patients as compared to healthy controls (53.75±15.25 Vs 82.58±18.04, p= 0.007). Percentage of NK cells expressing granzyme was higher in post TB with sequelae patients as compared to post TB without sequelae patients [28.75 (21.48-35.08) Vs. 4.35 (2.67-17.6), p=0.006] while percentage of NK cells expressing perforin was comparable between all the groups. <bold>Conclusion:</bold> Post Tuberculosis pulmonary sequelae is associated with decreased number of NK cells but increased expression of granzyme in these cells.