Phenotypic and functional characterization of bovine mucosal associated invariant T (MAIT) cells

Abstract

Abstract Mucosal associated invariant T (MAIT) cells are innate-like T cells that are prevalent in the blood and tissues of many mammalian species. MAIT cells recognize small metabolites derived from the riboflavin pathway that are presented by the highly conserved MHC-related protein-1 (MR1). MAIT cells have been described to play a proinflammatory role during several viral and bacterial diseases in humans and in rodent models. While MAIT cells have been described in cattle at the transcriptional level, little is known about the phenotype or function of this population in the bovine during steady-state or disease conditions. Here, using tetramers that bind to the MR1-restriced T cell receptors on MAIT cells, we investigated the frequency and phenotype of MAIT cells in the peripheral blood and bronchoalveolar lavage of healthy calves and animals with respiratory disease. We determined that cattle have 2 subsets of MAIT cells, defined by their expression of CD8; that bovine MAIT cells have the capacity to secrete IFNγ and IL-17 in response to mitogen stimulation; and that the frequency of MAIT cells in the bronchoalveolar lavage increases in the context of respiratory infection, suggesting that MAIT cells may play an important role in host defense in the respiratory tract of cattle.