Differential specific humoral response of susceptible and resistant mice infected with Mycobacterium lepraemurium.

C57BL/6 and BALB/c mouse strains were infected intraperitoneally with 10(8) Mycobacterium lepraemurium (MLM). At various stages of the infection, MLM-specific IgM, IgG, IgG1 and IgG2a serum antibodies were assessed. Anti-MLM antibody response varied markedly in both strains, in terms of antibody titres, Ig class distribution and kinetics of antibody secretion. C57BL/6 mice, which show intermediate resistance to MLM infection, presented the higher titres of IgM and IgG specific antibody, but without anti-MLM IgG1 detectable production. On the other hand, BALB/c susceptible strain showed a delayed but high IgG1 antibody production. Since it has been reported that Th2 lymphocyte subset modulate IgG1 antibody production, our results may reflect a differential activation of Th1 and Th2 cell subsets in both strains during a MLM infection.