Enhanced innate CD161+ T cell responses in mucosal tissues of nonhuman primates

Abstract

Abstract Innate T cells recognize non-peptide antigens presented by non-classical MHC molecules, such as CD1 and MR1. The three major populations within the innate T cell group, namely, γδ T cells, MAIT cells, and NKT cells express high levels of the C-type lectin molecule CD161. To understand the significance of CD161 expressing innate T cells in mucosal immunity, we investigated the phenotype and functions of these cells in mucosal tissues, lymph nodes and blood of rhesus macaques. The frequency of CD161+ T cells was higher in the lungs and colonic mucosa (9.4%±3.8 and 6.2%±1.9) in comparison to peripheral blood (2.9%±1) and mesenteric lymph nodes (0.5%±0.3). Regardless of the tissue compartment, 30 to 80% of the CD161+ T cells comprised of γδ T cells and TCR Vα 7.2+ MAIT cells in approximately equal proportions. However, only 1 to 6% consisted of CD1d tetramer+ NKT cells. Moreover, the mucosal tissue CD161+ T cells displayed a highly activated phenotype based on CD69 and HLA-DR expression in comparison to blood and lymph node cells. HMBPP stimulated γδ T cells from lungs and colonic mucosa produced significantly higher amounts of IFN-γ, Perforin and IL-17 than those in blood. Similarly, E.coli stimulated MAIT cells from mucosal tissues produced significantly higher amounts of IFN-γ and IL-17 than those in blood. The enhanced Th1 and Th17 type effector functions of mucosal innate T cells along with their cytotoxic potential suggests that they can mount early immune responses to mucosal pathogens like HIV and Mtb prior to the development of adaptive immune responses and thereby play a role in the initial control of pathogen burden/dissemination.