After intradermal injection of 10(7) promastigotes of a particular isolate of the intramacrophage protozoan parasite, Leishmania tropica, the development of disease (cutaneous lesions) is much more severe in BALB/c than in three other mouse strains, C57BL/6,C3H/He and CBA/H. Using fixed promastigotes and 125I-labelled protein A in a solid-phase radioimmunoassay (RIA), titres of antibody were shown to increase up to about day 50 of infection. However, titres were not markedly different in BALB/c mice compared with the other three resistant strains, although antibody levels were highest in sera from the diseased BALB/c mice at late time points. Using isotype-specific antisera in the RIA, and sera from the day 50 time point, the isotype distribution of anti-promastigote antibodies was not noticeably different in sera from mice of the four genotypes with IgG1 and IgG2a (+/- IgG2b) antibodies predominating. It is concluded that differences in susceptibility to disease in this murine model of cutaneous leishmaniasis do not correlate with any decrease or increase in any particular antibody response to the promastigote.
