Portal system peculiarities may contribute to resistance against schistosomes in 129/J mice.

Using the technique of latex microsphere injection into a mesenteric vein, evidence has been obtained for a 'leaky' portal system in 129/J mice maintained in this institute (WEHI 129/J) and also in C57BL/6 mice. Thus, 20-microns beads injected into the portal venous system of BALB/c and (BALB/cx129/J)F1 mice are trapped efficiently in the liver whereas in many 129/J and C57BL/6 mice the bulk of the injected beads is found in the lungs. Peculiarities in the hepatic portal system may thus contribute to resistance of WEHI 129/J mice (and to a lesser extent C57BL/6 mice) to infection with Schistosoma mansoni and S. japonicum. The possibility is raised by the data that increased access to, or residency times in, the lungs increases opportunities for expression of anti-schistosome immune responses and, in particular, the effects of recently described T-cell-initiated inflammatory responses in this organ. The variability within groups of WEHI 129/J and C57BL/6 mice in susceptibility to schistosomes as well as hepatic trapping of injected microspheres suggests that an infection of unknown type, proposed by others, contributes to the several peculiarities that have been described in at least 129/J mice.