Immunophenotypic characterization of peripheral T lymphocytes in Mycobacterium

 tuberculosis infection and disease
The cellular immune response probably plays a pivotal role in determining the clinical outcome after exposure to Mycobacterium tuberculosis. We used multi‐parameter flow‐cytometry to evaluate the distribution of T‐lymphocyte subsets during infection and disease caused by M. tuberculosis. Samples were obtained from 71 volunteers to identify the T CD4+ and CD8+ lymphocyte numbers, and the activation plus memory/naïve phenotypes, as defined by CD38, HLA‐DR, CD45RA and CD27 markers. Subjects were divided into 18 healthy volunteers without detectable reaction to purified protein derivative (PPD−), 18 health care workers with a recent conversion to PPD, 20 patients with active pulmonary tuberculosis (TBC) and 15 patients with treated TBC at 6 months of therapy. By multiple‐comparison analyses, the T CD4+ lymphocyte number of the TBC group was lower than the PPD– group (P < 0·05). This difference was apparently lost after treatment. The higher and the lower number of naïve T CD4+ cells was observed in the PPD– and TBC group, respectively. CD8+ T lymphocytes were also statistically different among the four groups (P = 0·0002), lower in the TBC group (P < 0·05). CD8+ T lymphocyte activation was evaluated by the CD38 and HLA‐DR surface expression. The percentage distribution of these markers was statistically different between the four groups (P = 0·0055). TBC patients had a higher percentage of CD38+ cells and mean fluorescence index, suggesting an overall increase of cell activation. These results suggest that peripheral T lymphocytes reflect cellular activation during TBC, along with possible redistribution of naïve, memory/effector and late differentiated memory/effector phenotypes in the peripheral blood after infection and disease caused by M. tuberculosis.