To investigate the influence of genetic differences in the MHC on susceptibility to
avian coccidiosis, M5.1 and M15.2 B-haplotype-disparate Fayoumi chickens were orally
infected with live Eimeria maxima oocysts, and BW gain, fecal oocyst production, and
expression of 14 immune-related genes were determined as parameters of protective
immunity. Weight loss was reduced and fecal parasite numbers were lower in birds of
the M5.1 line compared with M15.2 line birds. Intestinal intraepithelial lymphocytes
from M5.1 chickens expressed greater levels of transcripts encoding interferon-gamma
(IFN-gamma), interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12, IL-15, IL-17A, inducible
nitric oxide synthase, and lipopolysaccharide-induced tumor necrosis factor-alpha
factor and lower levels of mRNA for IFN-alpha, IL-10, IL-17D, NK-lysin, and tumor
necrosis factor superfamily 15 compared with the M15.2 line. In the spleen, E. maxima
infection was associated with greater expression levels of IFN-gamma, IL-15, and IL-8
and lower levels of IL-6, IL-17D, and IL-12 in M5.1 vs. M15.2 birds. These results
suggest that genetic determinants within the chicken MHC influence resistance to E.
maxima infection by controlling the local and systemic expression of immune-related
cytokine and chemokine genes.