Bovine gamma delta T cells and the function of gamma delta T cell specific WC1 co-receptors

• We review the importance of and history of research on bovine γδ T cells.
• Bovine γδ T cells are similar to and different from human γδ T cells.
• γδ T cells play an important role in the bovine response to Mycobacteria spp.
• WC1/CD163 SRCR proteins appear in the genomes of birds, reptiles, fish and mammals.
• WC1 is a hybrid coreceptor/PRR in bovine γδ T cells.

The study of γδ T cells in ruminants dates to the discovery of the γδ TCR in humans and mice. It is important since cattle offer an alternative model to the mouse for evaluating the role of γδ T cells in zoonotic disease research and for control of disease reservoirs in non-human animals. In addition, maintaining the health of cattle and other members of the order Artiodactyla is critical to meet the global human need for animal-source protein. In this review, we examine the bovine γδ T cell responses to Mycobacteria, which infects a third of the human population, and bovine γ and δ TCR diversity and the relationship to the TCR of human mycobacteria-responsive γδ T cells. We review the utilization of the γδ T cell specific scavenger receptor cysteine-rich (SRCR) glycoproteins known as WC1, and that are part of the CD163 family, which function as both γδ T cell activating co-receptors and pattern recognition receptors (PRR) for bovine γδ T cells and highlight the presence and evolution of this multigenic array, with potential for the same function, in birds, reptiles, jawless and bony fishes, and prototherian and eutherian mammals.