Strain difference of delayed-type hypersensitivity to BCG and its genetic control in mice

Delayed-type hypersensitivity to BCG was remarkably different in two inbred strains of mice, SWM/Ms and C3H/He, when measured by the spleen index, the disappearance of peritoneal macrophage, or the footpad reaction. High responsiveness in the SWM/Ms strain appeared to be dominant over low responsiveness in the C3H/He strain. Results of the footpad reaction test if F1, F2, and backcross hybrids of these two strains of mice suggested that the delayed-type hypersensitivity was mainly controlled by a gene which was transmitted under Mendel's laws and was possibly non-H-2 linked. The spleen cells and their nylon wool nonadherent fraction from BCG-infected C3H/He mice were not reactive to purified protein derivative in vitro, whereas both the spleen cells and the nylon wool nonadherent fraction from BCG-infected SWM/Ms mice reacted well to purified protein derivative. Possible mechanisms of the different responses in the delayed-type hypersensitivity to BCG were discussed.