FLOW-CYTOMETRIC ASSESSMENT OF INTRACELLULAR INTERFERON-GAMMA PRODUCTION IN HUMAN CD4-CELLS ON MYCOBACTERIAL ANTIGEN STIMULATION(VE T)

Interferon-gamma (IFN-gamma) has been considered to be a critical prot ective immunomodulatory component against Mycobacterium tuberculosis ( M. tb.) infection. In this study T-cell proliferation and IFN-gamma pr oduction upon stimulation with M. tb. were assessed in patients of pul monary tuberculosis and healthy contacts. The studies mere based on ly mphocyte transformation test and detection of intracellular IFN-gamma 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-gamma on M. tb. stimulation showed a proportional increase in the CD4 + ve T-ce ll population. The increase was maximal between 96-120 h of culture, I n healthy contacts the number of IFN-gamma expressing CD + ve T-cells increased to 2.5 to 41 x 10(4) cells/ml in M. tb. stimulated cultures compared to control cultures (0.1-15 x 10(4)). In contrast patients sh owed no/marginal increase in CD4 + ve T-cell population expressing int racellular IFN-gamma. Thus the lack of induction of IFN-gamma in CD4 ve T-cells in patients could be a critical shortcoming in their abili ty to combat tubercle bacilli infection.