Immunity to trichinella spiralis

The major part of this work was concerned with the mechanism of protective immunity which acts against the parenteral phase of a Trichinella spiralis infection in mice. Passively transferred immune serum always gave strong protection, to recipients, against an intravenous challenge of newborn larvae, regardless of whether the donor animals were sensitized by single, multiple, full or parenteral infections of T. spiralis. Small doses of immune serum gave significant protection, against challenge, to mice. Sensitized spleen cells and mesenteric lymph node cells, taken from infected donors, varied in their ability to protect recipient mice against challenge. Immune serum was only effective when transferred before a parenteral challenge, suggesting that it affected the newborn larvae and not the muscle larvae. The protective factors in immune serum appeared seventeen days after a single parenteral infection was given; they became progressively more protective after this time and there was evidence of their presence in serum taken five months after infection. The serum factors were protective in the absence of effector T-cells but whether they acted alone, against newborn larvae, or required the cooperation of non-specific cells was not fully established. Genetical studies on the ability of CBA and NIH mice to expel intestinal T. spiralis were made. CBA mice responded poorly to infection whereas NIH mice responded well. Cross breeding between the strains and back crosses with the first generation progeny of these showed that the responder characteristic of NIH mice was dominant and its inheritance was polygeneic. The ability to expel adult worms was not linked to the genes coding for the colour or sex of the mice.