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The C57 BL/6 mouse strain is resistant to Leishmania (L.) major infection and, unlike susceptible BALB/c, develops small self-healing cutaneous lesions. The specific antibody responses of C57 BL/6 and BALB/c mice were previously characterized by the predominance of IgG2a ('resistant' isotype associated with Th1) and IgG1 ('pathogenic' isotype associated with Th2) antibodies, respectively. In this study, we looked for the presence of antigens able to elicit an exclusive or predominant IgG1 production during the early stages of C57 BL/6 lesion development and checked whether they are recognized or not by BALB/c mice. We demonstrate first that IgG2a predominance in C57 BL/6 sera occurs only late after infection, whereas in BALB/c, IgG1 antibodies dominate mostly in the early stages. Interestingly, soon after inoculation of live amastigotes, C57 BL/6 displayed an exclusive IgG1 reactivity against particular L. major antigens but with MWs different from those identified in BALB/c. Furthermore, mice immunized with killed amastigotes displayed striking differences in their immunodetection profiles, particularly for the IgG1 isotype. Taken together, the observed differences in the specific antibody repertoires between infected mice resulted, at least in part, from immunological events independent from those triggered by the replicating parasite, and bring new insights into the selection of future vaccine candidates. [ABSTRACT FROM AUTHOR]