Oligo-B, but not Oligo-B negative augmented the prime BCG vaccination. BCG-vaccinated or unvaccinated 30-week aged mice were subcutaneously injected with 50 μg of booster (Oligo-B or Oligo-B-negative), every 2 weeks. Splenocytes prepared from each mouse 2 weeks after 3-times boosting were incubated in a 24-well plate, at a concentration of 5 × 105 cells per well. Cells were stimulated with 10 μg/ml of PPD (solid column) or PBS (open column) and incubated for 48 h. Then, supernatants were collected and the concentration of IFN-γ was measured by ELISA. Results are shown as mean ± SD from groups of three mice. * p < 0.05, N.S.: not significant.