Lymphocyte, antibody and cytokine responses during concurrent infections between helminths that selectively promote T-helper-1 or T-helper-2 activity.

The influence of Trichinella spiralis on infections with Trichuris muris was studied in non-responder B10.BR mice. Mice infected only with T. muris were unable to expel parasites and had many adult worms 35 days later. Infection with 300 larvae of T. spiralis, given seven or 14 (but not 28) days after T. muris, enabled mice to expel up to 90% of T. muris; expulsion of T. spiralis was not altered. Concurrently infected mice produced less T. muris-specific IgG2a antibody than mice infected with T. muris only, and showed higher proliferative responses when spleen and mesenteric lymph node cells were cultured in vitro with T. muris antigens. When T. spiralis was present mucosal mast cells were generated in T. muris-infected mice, whereas almost no mast cells were seen with only T. muris. Lymphocytes from doubly-infected mice produced significantly more interleukin 4 and 5 (IL-4, IL-5) and significantly less interferon-gamma (IFN-gamma) when stimulated in vitro with Concanavalin A (Con-A) than cells from mice infected with T. muris only. These data demonstrate that B10.BR mice, which in single infections produce a Th1 response to T. muris and develop no protective immunity, can mount a protective T-helper-2 (Th2) response and expel T. muris when concurrently infected with the 'Th2-inducing' nematode T. spiralis.