Regulatory T Cell Properties of Chicken CD4+CD25+ Cells

Abstract

Chicken CD4+CD25+ cells were characterized for mammalian regulatory T cells’ suppressive and cytokine production properties. Anti-chicken CD25 mAb was produced in mice and conjugated with a fluorescent tag. The specificity of the Ab against chicken CD25 was confirmed by evaluating Con A-induced CD25 upregulation in thymocytes and by quantifying the CD25 mRNA content of positive and negative cells identified by anti-chicken CD25 Ab. The percentage of CD4+CD25+ cells, expressed as a percentage of CD4+ cells, in thymus and blood was ∼3–7%, in spleen was 10%, and in cecal tonsil, lung, and bone marrow was ∼15%. Bursa had no detectable CD4+CD25+ cells. CD25+ cells were mostly CD4+ in the thymus, whereas in every other organ studied, CD25+ cells were distributed between CD4+ and CD4− cells. Chicken thymic CD4+CD25+ cells did not proliferate in vitro in the absence of recombinant chicken IL-2 (rCIL-2). In the presence of rCIL-2, PMA plus ionomycin or Con A stimulated CD4+CD25+ cell proliferation, whereas anti-CD3 plus CD28 did not stimulate CD4+CD25+ cell proliferation. Naive CD4+CD25+ cells had 29-fold more IL-10 mRNA and 15-fold more TGF-β mRNA than the naive CD4+CD25− cells. Naive CD4+CD25+ had no detectable IL-2 mRNA. Both naive and PMA plus ionomycin-stimulated thymic CD4+CD25+ cells suppressed naive T cell proliferation. The suppressive properties were partially contact dependent. Supplementing CD4+CD25+ cell coculture with rCIL-2 reversed the suppressive properties of CD4+CD25+ cells. Chicken CD4+CD25+ cells have suppressive properties similar to that of mammalian regulatory T cells.