Effect of dose, route, and schedule of BCG on antibody titer and survival of murine skin grafts across a weak histocompatibility barrier

Skin was transplanted from male to female C57BL/6JRC mice. Bacillus Calmette‐Guérin (BCG) was administered once subcutaneously, intramuscularly, or intraperitoneally either 14 days prior to grafting or on the day of grafting in a dose of 5 × 105, 5 × 106, or 5 × 107 microorganisms. Serum antibody to BCG was assayed using complement fixation. There was a linear inverse relation between skin graft rejection and dose of BCG (p < .01) such that the lowest dose of BCG was the most effective. The IM and SQ, routes were more effective than the IP route. Schedule did not have significant effect on skin graft survival. Time to appearance of antibody correlated directly with dose. The prolonged survival of skin grafts combined with early appearance of antibody to BCG suggested that high doses of BCG could result in antigenic competition.