HLA-C and Nematoda infectious disease: Therefore, owing to the importance of the MHC molecules in antigen recognition and presentation [25-27], and the fact that an allele of the MHC-DRB1 locus has been associated with increased nematode resistance in sheep [10,28,29], it is plausible that MHC genes play a key role in determining the outcome of the immune response and nematode infection in general.