Flowcytometric assessment of intracellular interferon-γ production in human CD4 + ve T-cells on mycobacterial antigen stimulation.

ABSTRACT

Interferon- (IFN-γ ) has been considered to be a critical protective immunomodulatory component against Mycobacterium tuberculosis (M. tb.) infection. In this study T-cell proliferation and IFN-γ production upon stimulation with M. tb. were assessed in patients of pulmonary tuberculosis and healthy contacts. The studies were based on lymphocyte transformation test and detection of intracellular IFN-γ production by CD4 + ve T-cells by flowcytometry. Patients showed lower levels of proliferation, the stimulation index being in the range of 2·17 1·1 (mean + SD) compared to the contacts (SI = 4·59± 1·6) (P < 0·01). The kinetics of intracellular induction of IFN-γ on M. tb. stimulation showed a proportional increase in the CD4 + ve T-cell population. The increase was maximal between 96-120 h of culture. In healthy contacts the number of IFN-γ expressing CD + ve T-cells increased to 2·5 to 41 × 104 cells/ml in M. tb. stimulated cultures compared to control cultures (0·1 —15 × 104). In contrast patients showed no/marginal increase in CD4 + ve T-cell population expressing intracellular IFN- γ Thus the lack of induction of IFN in CD4 + ve T-cells in patients could be a critical shortcoming in their ability to combat tubercle bacilli infection.