PD-1 regulates KLRG1+ group 2 innate lymphoid cells

Group 2 innate lymphoid cells (ILC-2s) regulate immune responses to pathogens, allergens, tissue remodeling and metabolic homeostasis in response to cytokines. Positive regulation of ILC-2s through ICOS has been recently elucidated but co-receptor mediated negative regulatory axis is yet to be defined. We demonstrate that PD-1 is an important negative regulator of KLRG1+ILC-2 function in both mice and humans. Increase in KLRG1+ ILC-2 cells numbers were attributed to an intrinsic defect in PD-1 signaling, which resulted in enhanced STAT5 activation. During Nippostrongylus brasiliensis infection, a significant expansion of KLRG1+ ILC-2 subsets occurred in pdcd1-/- mice and on adoptive transfer, pdcd1-/- KLRG1+ ILC-2s significantly reduced worm burden. Furthermore, blocking antibody to PD-1 increased KLRG1+ ILC-2 cell number and reduced disease burden. Therefore PD-1 is an important negative regulator and is vital for maintaining the number and hence function of KLRG1+ ILC-2s. Microarray for wildtype and Pdcd1 knockout mice, each with three replicates