Sex differences and cross-immunity in DBA/2 mice infected with L. mexicana and L. major

Female DBA/2 mice were found to be highly resistant to Leishmania mexicana and rarely developed lesions even when inoculated subcutaneously with high numbers (5 x 10(6] of amastigotes. Male DBA/2 mice, on the other hand, were much more susceptible to this parasite and often developed non-healing lesions even when inoculated subcutaneously with comparatively few (5 X 10(4] amastigotes. Conversely, although both male and female DBA/2 mice developed ulcerating lesions when inoculated subcutaneously with L. major amastigotes, lesions invariably healed in males but did not heal in females. Male DBA/2 mice recovered from L. major infection subsequently were found to be resistant to subcutaneous challenge with L. mexicana. Conversely female DBA/2 mice that had failed to develop lesions when infected with L. mexicana developed lesions which healed following subcutaneous challenge with L. major. Thus there is bilateral cross-immunity between L. mexicana and L. major in DBA/2 mice which overrides differences in sex-determined susceptibility to both organisms.

The use of host strain variation to assess the significance of mucosal mast cells in the spontaneous cure response of mice to the nematode Trichuris muris

A proportion of DBA/2 mice do not reject the large intestinal nematode parasite Trichuris muris. In this strain and the early rejecting NIH and the late rejecting CBA/Ca strains the kinetics of the mast cell accumulation in a primary infection were similar with peak mast cell numbers being recorded on day 20 post-infection. Comparisons between rejector and non-rejector DBA/2 mice showed no differences in the mast cell accumulation. There was no rise in mast cell numbers in response to a secondary infection, in either the NIH or CBA/Ca strains, for at least 3 days after the infection had been expelled. It is suggested that mucosal mast cell accumulation is not induced by a simple response to parasite factors, that the cells are not directly involved in the expulsion of T. muris and that any role they play in the spontaneous cure response is subject to more complex control.

Helminth parasites of conventionally maintained laboratory mice

The spectrum of intestinal parasites present in the Swiss Webster, C57B1/6 and DBA/2 mice strains from different animal houses was identified and prevalences compared. Three parasites were observed during the course of this study, namely the cestode Vampirolepis nana (Siebold, 1852) Spasskii, 1954 (= Hymenolepis nana) and the nematodes Aspiculuris tetraptera (Nitzsch, 1821) Schultz, 1924 and Syphacia obvelata (Rudolphi, 1802) Seurat, 1916. The scope of this investigation has been widened to also include morphometric data on the parasites, to further simplify their identification, since the presence of helminths in laboratory animals is regarded as a restricting factor for the proper attainment of experimental protocols.

Strain-dependent differences in susceptibility of mice to experimental Angiostrongylus costaricensis infection

Experimental Angiostrongylus costaricensis infection was carried out in inbred strains of mice (C57BL/6 BALB/c, DBA/2 and C3H/He). All strains became infected with this parasite. Marked differences in mortality and in worm burden were found among inbred strains of mice tested. A significant reduction was shown in worm length from mice compared to that from cotton rats.

Host specificity of Giardia muris isolates from mouse and golden hamster

One isolate of Giardia muris from a naturally infected laboratory mouse (Mus musculus) and one from a naturally infected golden hamster (Mesocricetus auratus) were passaged three times by the inoculation of ten cysts (the minimal infectious dose) into barrier-maintained homologous hosts. Both of the resultant isolates were tested for infectivity by intragastric inoculation of 3-5 x 10(5) cysts into 40 mice (2 inbred strains), 40 rats (2 inbred strains), and 19 golden hamsters (1 outbred strain). Rats were not susceptible to infection with either isolate. Mice and golden hamsters did develop infections following their inoculation with the heterologous isolates. The mean intensity of heterologous infections with the hamster isolates was significantly lower than that of homologous infections. The mouse isolate induced a higher mean intensity of infection in hamsters as compared with homologous recipients. The mean intensity of infections induced by both isolates was greater in male hamsters than in females.

[Sensitivity of inbred mice to toxoplasma of virulent and nonvirulent strains according to parasitological study data]

Genetic peculiarities of mice were studied in regards to their susceptibility to toxoplasms. Differences in susceptibility to little virulent toxoplasms in mice of 9 different lines are shown, which manifest at all stages of the infection process or only at acute or chronic stages. The susceptibility of 6 lines of mice to virulent toxoplasms was found to be equally high.