Priming of a beta-galactosidase (beta-GAL)-specific type 1 response in BALB/c mice infected with beta-GAL-transfected Leishmania major

To determine whether an ongoing response to Leishmania major would affect t he response to a non-crossreacting, non-leishmanial antigen, susceptible BA LB/c mice and resistant C3H mice were infected with L. major parasites expr essing Escherichia coli beta-galactosidase (beta-GAL); this parasite was de signated L, major-beta GAL, BALB/c and C3H mice responded to infection with L. major-beta GAL by mounting a CD4 T-cell response to both parasite antig ens and to the reporter antigen, beta-GAL. The phenotypes of these T cells were characterized after generating T-cell lines from infected mice. As exp ected, BALB/c mice responded to infection with L. major-beta GAL by produci ng interleukin 4 in response to the parasite and C3H mice produced gamma in terferon (IFN-gamma) in response to the parasite and beta-GAL. Interestingl y, however, BALB/c mice produced IFN-gamma in response to beta-GAL. Taken t ogether, these results demonstrate that priming of IFN-gamma-producing cell s can occur in BALB/c mice despite the fact the animals are simultaneously mounting a potent Th2 response to L. major.