Inverted CD4+/CD8+ T cell ratio in Boran (Bos indicus) cattle

•Inverted T helper (CD4)/Cytotoxic T cell (CD8) ratio in Boran cattle.•Higher absolute numbers of circulating CD8 T cells in Boran cattle than EASZ, N'dama, Nelore and Holstein-Friesian.•Female cattle have significantly higher CD4/CD8 ratio than male cattle. The CD4+/CD8+ ratio is used as a marker of the immune regulation of T cell balance. When the ratio in peripheral blood is less than 1, this is considered an indication of immune suppression in an individual. Previous work on bovine Peripheral Blood Mononuclear Cells (PBMC) has consistently reported a ratio ≥1 as seen in other mammalian hosts, i.e. higher circulating CD4+ cell numbers than CD8+ cell numbers. However, a consistent inverted CD4+/CD8+ ratio (