T cells in mesenteric and subcutaneous adipose tissue of Holstein-Friesian cows

The importance of immune cells present in the adipose tissue to metabolic homeostasis has been increasingly recognized. Nevertheless, in bovines few studies have so far addressed the immune cell populations resident in this tissue. Here we developed an eight-colour flow cytometry panel to address T cell populations present in bovine adipose tissue. Our results showed that γδ T cells, CD4⁺ and CD8⁺ CD3⁺ non-γδ T cells, as well as NK cells, are present in the mesenteric and subcutaneous adipose tissue of Holstein-Friesian cows. The frequency of both γδ T cells and CD8⁺ non-γδ T cells was found higher in mesenteric than in subcutaneous adipose tissue. The majority of T cells in adipose tissue presented a CD45RO⁺CD62L^- phenotype, characteristic of effector memory cells, and the frequency of these cellular populations was higher than in the blood. The ratio of CD4⁺ T cells over CD8⁺ T cells was similar between subcutaneous and mesenteric adipose tissue but different from the one found in blood. Overall, our results highlight particular phenotypic characteristics of bovine adipose tissue T cell populations.