The Ity/Lsh/Bcg gene significantly affects mouse resistance to Mycobacterium lepraemurium.

Mouse resistance to infection with Mycobacterium lepraemurium was measured by counting the total number of intact acid-fast bacilli in the spleen 8 weeks after i.v. injection of a standard inoculation. The effect of Ityr on resistance to M. lepraemurium was confirmed and the results extended to two Ityr strains of mice, A and C57L, not previously tested. Resistance to M. lepraemurium was also examined in the F1, backcross and F2 generations of BALB/c X CBA crosses, and in the congenic strain B10.LLshr that is Ityr. In all experiments the results were consistent with the view that resistance to M. lepraemurium is significantly affected by a gene close to or identical to the Ity/Lsh/Bcg gene on mouse chromosome 1. Sex had a marked effect on resistance to M. lepraemurium, so that the males of some genetically resistant strains were almost as susceptible as some genetically susceptible females.