Changes in immune-related gene expression and intestinal lymphocyte subpopulations following Eimeria maxima infection of chickens

Coccidiosis, a major intestinal parasitic disease of poultry, induces a cell-mediated immune response against the etiologic agent of the disease, Eimeria. In the current study, the expression levels of gene transcripts encoding pro-inflammatory, Th1, and Th2 cytokines, as well as chemokines were measured in intestinal intraepithelial lymphocytes (IELs) after Eimeria maxima infection. In addition, changes in IEL numbers were quantified following E. maxima infection. Transcripts of the pro-inflammatory and Th1 cytokines IFN-γ, IL-1β, IL-6, IL-12, IL-15, IL-17, and IL-18 were increased 66- to 8 × 107-fold following primary parasite infection. Similarly, mRNA levels of the Th2 cytokines IL-3, IL-10, IL-13, and GM-CSF were up-regulated 34- to 8800-fold, and the chemokines IL-8, lymphotactin, MIF, and K203 were increased 42- to 1756-fold. In contrast, IFN-α, TGF-β4, and K60 transcripts showed no increased expression, and only the level of the Th2 cytokine IL-13 was increased following secondary E. maxima infection. Increases in intestinal T cell subpopulations following E. maxima infection also were detected. CD3+, CD4+, and CD8+ cells were significantly increased at days 8, 6, and 7 post-primary infection, respectively, but only CD4+ cells remained elevated following secondary infection. TCR1+ cells exhibited a biphasic pattern following primary infection, whereas TCR2+ cells displayed a single peak in levels. Taken together, these data indicate a global chicken intestinal immune response is produced following experimental Eimeria infection involving multiple cytokines, chemokines, and T cell subsets.