Mitogen-induced DNA synthesis in various mouse strains infected with a large or small dose of murine leprosy bacilli.

Mice of the C57BL strain have been shown to be rather resistant to infection with Mycobacterium lepraemurium, whereas C3H mice are highly susceptible. Accordingly, it seemed to be somewhat paradoxical that enhanced antibody formation coupled with a depressed state of cell-mediated immunity as expressed by negative macrophage migration inhibition tests was observed not in C3H but in C57BL mice when they were inoculated with a large dose of murine leprosy bacilli, as reported in our previous studies. In the present study mitogen-induced DNA synthesis by lymph node cells was examined in 16 strains of mice which had been infected with a large or small dose of M. lepraemurium. According to the response to two kinds of T-cell mitogens, these mouse strains could be roughly divided into three groups consisting of two polar groups represented by C57BL/6J and C3H/HeN, respectively, and one intermediate between them. Furthermore, both humoral and cellular immune responses so far observed in C57BL and C3H mice were substantiated by DNA synthesis by lymph node cells harvested from these strains of mice and then exposed in vitro to B-cell and T-cell mitogens, respectively. However, no correlation was found between mitogen-stimulated DNA synthesis by these 16 strains of mice and their H-2 specificity.