Analysis of local T lymphocyte subsets upon stimulation with intravesical BCG: a model to study tuberculosis immunity

Cell-mediated immune response can control tuberculosis infection. A significant role for immune cells like CD4, CD8 and gammadelta T lymphocytes have been recognized, but little is known about the kinetics of activation and accumulation of these cells in course of Tuberculosis infection in humans. This is due to both the difficult to access to human lung and the fact that most subjects are examined in different periods of infection which may condition T cell changes. To overcome these problems, we have used intravesical BCG (Bacillus Calmette-Guerin) treatment for preventing the recurrences of bladder cancer as an in vivo experimental model of human tuberculosis infection. 20 male caucasian patients with proven bladder superficial transitional cell carcinoma treated with transurethral resection followed by six weekly intravesical instillations of BCG (T0-T6) were enrolled. Changes in T lymphocyte subsets were assessed by flow cytometry in the bladder wash recovered after each BCG instillation. Our study shows that the action of BCG appears to be T cell dependent. Lymphocytes increase at any new instillation and tend towards the reduction with the suspension of the stimulus. BCG induces a massive increase in the proportion of CD4 Th1 subset followed by an increase in gammadelta T cells, while no significant variation for CD8 and NK cells is found. Our results suggest that BCG infection model represents a valid experimental tool to study the immunological events evoked in vivo by Mycobacterium tuberculosis in humans at the site of infection.