Differential cytokine gene expression in CD4⁺ and CD8⁺ T cell subsets of calves

The distinct patterns of cytokine expression in CD4⁺ and CD8⁺ T cells are well understood in mice and humans. However, little information is available about cytokine expression in bovine CD4⁺ and CD8⁺ T cells. In this study, mRNA expression of 19 different cytokines was analyzed in CD4⁺ and CD8⁺ T cells of calves with or without Concanavalin A (Con A) stimulation. CD4⁺ and CD8⁺ T cell populations were enriched to 98% purity by positive selection using magnetic cell sorting (MACS). CD4⁺ T cells spontaneously expressed the mRNAs of interleukin-1α (IL-1α), IL-1β, IL-2, IL-6, IL-7, IL-8, IL-10, IL-18, IFN-γ, TNF-α, TNF-β and TGF-β, and augmented the mRNA expression of IL-10, IFN-γ and TNF-β after Con A stimulation. The mRNAs of IL-3, IL-4, IL-5, IL-13 and GM-CSF were newly expressed in Con A-stimulated CD4⁺ T cells. CD8⁺ T cells displayed spontaneous mRNA expression of IL-6, IL-18, TNF-α, TNF-β and TGF-β, and newly expressed the mRNA of IL-2, IL-7, interferon-gamma (IFN-γ) and GM-CSF after Con A stimulation. It was found that CD4⁺ T cells expressed the mRNA of 17 cytokines except for IL-12 and IL-15, while CD8⁺ T cells expressed only the mRNA of 9 cytokines after Con A stimulation. The profile of cytokine mRNA expression was substantially different in the CD4⁺ and CD8⁺ T cells of calves, indicating that CD4⁺ T cells can be distinguished from CD8⁺ T cells by the cytokine gene expression of IL-1α, IL-1β, IL-3, IL-4, IL-5, IL-8, IL-10 and IL-13. Differential cytokine expression between CD4⁺ and CD8⁺ T cells serve to interpret an individual function of T cell subsets in the immune system of calves.