Tuberculin specific T cell responses in BCG vaccinated children.

The effector mechanisms of BCG protection were examined 5-7 years after vaccination. The in vitro lymphoproliferation, following stimulation with tuberculin, in normal, (A) vaccinated and (B) unvaccinated children and children with tuberculosis (C), were assayed. The mean stimulation index (SI) of lymphocyte transformation in normal subjects were significantly (P < 0.05) higher than those with tuberculosis. The ratio of tuberculin-specific CD4 to CD8 cells in short-term cultures were significantly (P less than 0.05) higher in the vaccinees. In group (A), 70 % had positive ratios as against 20 %and 0 %in groups (B) and (C), respectively. Secretion of IL-2 by the cells was significantly (P < 0.05) high in the vaccinated. None of the unvaccinated children had positive levels of IL-2. The vaccinees also had highly significant (P < 0.01) levels of IFN-)in the supernatants of cell-cultures, following tuberculin stimulation. In majority of the BCG vaccinated children, the stimulation of specific TH1 cells seem to be considerably high, in short-term in vitro cultures. While these responses were not so marked in the unvaccinated, they were almost totally absent in the patients.