Blok BA, de Bree LCJ, Diavatopoulos DA, et al. - Researchers explored the nonspecific immunological effects of Bacille Calmette-Guérin (BCG) and diphtheria-tetanus-pertussis (DTP)-containing vaccines on the immune response to unrelated pathogens. They conducted a randomized trial including 75 healthy, female, adult volunteers and assigned them to receive either BCG, followed by a booster dose of tetanus-diphtheria-pertussis inactivated polio vaccine (Tdap) 3 months later; BCG and Tdap combined; or Tdap followed by BCG 3 months later. On assessing ex vivo leukocyte responses to unrelated stimuli and pathogens, it was noted that Tdap vaccination results in short-term potentiation and long-term suppression of monocyte-derived cytokine responses, and short-term as well as long-term suppression of T-cell reactivity to unrelated pathogens. Vaccination with Tdap and BCG induced the modulation of heterologous immune responses. Concurrent or subsequent BCG vaccination partially restored the immunotolerance induced by Tdap to unrelated antigens.