Abstract
The influence of genes in the major histocompatibility complex (MHC) of the guinea pig on the susceptibility to infection with the parasitic nematode Trichostrongylus colubriformis was investigated. Back-cross analysis of 2 lines of guinea pigs suggests that genes that map in or near the I region of the guinea pig MHC influence susceptibility to infection by the parasite. However, other genes, possibily not linked to the guinea pig MHC, may also be required for the full expression of susceptibility.