Figure 1.

Previous exposure to BCG or Mtb induces cross-reactive T cells against NTM. PBMC from BCG-vaccinated and/or latent TB infected individuals (n = 6) were CFSE-labeled and stimulated with optimal concentrations of live BCG (Connaught) or MAV (ATCC 700898). On day 7, cells were restimulated with PMA/ionomycin and the total percentages of CFSE^lo (proliferating) and IFN-γ producing T cells were determined by flow cytometry. (A) Flow cytometry plots of a single volunteer. Lymphocytes gated on the basis of forward and side scatter and then regated on CD3⁺ cells were analyzed for CFSE and IFN-γ expression by use of FlowJo software. The number in the upper left quadrant of each dot plot refers to the percentage of CFSE^loIFN-γ⁺CD3⁺T cells detected after in vitro stimulation. (B) Composite data from 6 volunteers. Stimulation indices were calculated by dividing the absolute numbers of CFSE^loIFN-γ⁺CD3⁺ T cells in cultures containing BCG or MAV by the absolute numbers of CFSE^lo/IFN-γ⁺ CD3⁺T cells in medium-rested cultures. Stimulation with MAV led to expansion of effector T cells comparable to the level obtained with BCG stimulation (P > 0.05, Wilcoxon matched-pairs test). The bars show ranges and the lines show mean values. NS, not significant.