Genetic factors involved in murine susceptibility to experimental brucellosis

C57BL/6 are more resistant than DBA2 mice to Brucella suis 1330. This difference does not concern the blood clearance of the i.v. inoculated bacteria or the number of infective colonies in the spleen at very early stages but the splenic infection at later stages with maximal differences on day +7. The "resistance" character is inherited by F1 and back-crosses as a partially dominant character with polygenic control and a better expression of resistant factor(s) in females. This phenomenon of sex limitation is independent of male-female matings and therefore not sex-linked. Association of the "resistance" character with known genetic markers was investigated using (B6 X DB) X DB back-crosses, BALB/B, BALB/c, C3H/eb and C3H/HeJ mice. No correlation of "resistance" with Ig allotypes, the "d" coat color or the LPS genes was evidenced. On the other hand significant differences in the number of splenic colonies on day 7 were observed according to the H-2 haplotype or the "b" coat color phenotypes. These results are discussed in terms of: a) the partially common and partially independent genetic regulation of susceptibility to experimental brucellosis and antibody response to Brucella antigens; b) the possible importance of sex-dependent and MHC or chromosom 4-linked genetic factors for bacterial immunity.