Cytokine gene expression in splenic CD4+ and CD8+ T cell subsets of genetically resistant and susceptible chickens infected with Marekʹs disease virus

T cells from the spleens of B19/B19 and B21/B21 chickens infected with MDV JM-16 strain were fractionated by flow cytometry at 4, 10, 21 days post infection (d.p.i.). The expression of cytokine and viral genes (meq and glycoprotein B (gB)) was measured by real-time RT-PCR. It was determined that CD4+ and CD8+ T cells had both become infected with Marekʹs disease virus (MDV) in both chicken lines. There was significantly higher expression of meq in CD4+ T cells compared to CD8+ T cells at 10 and 21 d.p.i. Furthermore, at 10 and 21 d.p.i., there was a tendency for higher expression of meq in both T cell subsets of B19 chickens compared to those of B21 chickens. There were temporal changes in the expression of cytokines, interferon (IFN)-γ, interleukin (IL)-18, IL-6, and IL-10, in various T cell subsets. Among these changes, there was an increase in IL-10 expression in both T cell subsets at different time points, especially in the susceptible line at 10 and 21 d.p.i. Our results indicate that cytokines could be differentially induced by MDV in CD4+ and CD8+ T cell subsets and that IL-10 may play a role in the modulation of immune response to MDV. However, an association between cytokine gene expression in T cell subsets and resistance or susceptibility to MD was not established.