Natural killer cell receptor protein 1 (NKR-P1) molecules are C-type lectin-like receptors modulating cellular responses toward target cells expressing C-type lectin-like related (Clr) molecules. Although the function of the prototypic rat NKR-P1A receptor and its inhibitory counterpart NKR-P1B are known, little is known about NKR-P1F and NKR-P1G apart from their promiscuity for Clr ligands. Here we generated mAbs against both receptors for phenotypic and functional analyses in rat tissues. NKR-P1F induced redirected lysis and robust Ca 2+ signaling in NK cells, which were prevented by simultaneous engagement of NKR-P1G. NKR-P1G also inhibited NK-cell lysis of Clr transfectants. NKR-P1F was expressed by most NK cells and NKR-P1A + T cells in all tissues analyzed, and by many NKR-P1A − intestinal T cells, while NKR-P1G was expressed by subsets of these cells with highest prevalence in gut and liver. In the intraepithelial compartment, the proportion of NKR-P1A + and NKR-P1F + cells was high at birth and thereafter declined, while NKR-P1B + and NKR-P1G + cells increased with age. Expression levels were also modulated by cytokines, with an increase of NKR-P1B and NKR-P1G induced by inflammatory cytokines, and a reduction of NKR-P1A by TGF-β. The physiological impact of NKR-P1 receptors might thus be dependent on age, tissue, and inflammatory status.Keywords: C-type lectin-related molecules r NK-cell receptors r NKR-P1 r Rodent Additional supporting information may be found in the online version of this article at the publisher's web-site
IntroductionNatural killer (NK) cells are innate lymphoid cells with the ability to eliminate virally infected cells and transformed or allogeneic cells. They produce cytokines early in the immune response, and play an important role in shaping the immune response, e.g. in the context of inflammation and transplantation. These tasks are controlled by a wide range of receptors with different functions and ligands, such as Ly49 receptors, which recognize both classical and nonclassical MHC class I molecules, as well as MHC Correspondence: Dr. Lise Kveberg e-mail: lise.kveberg@rr-research.no class I-like virally encoded ligands [1][2][3]. Another family of MHCbinding receptors is the conserved NKG2/CD94 heterodimers, which bind the nonclassical MHC molecule HLA-E in human [4], its rodent homologue Qa-1 b in the mouse [5,6] and RT.BM1 in the rat [7]. Both the Ly49 and NKG2/CD94 receptor families contain inhibitory and activating members. NKG2D is a promiscuous activating receptor, recognizing several MHC class I-related ligands frequently upregulated upon cellular stress and associated with viral infection and malignant transformation [8].The activating NK cytotoxicity receptors react with several virus-derived and endogenous ligands [9,10].One of the earliest NK-cell receptors to be characterized was the NK-cell receptor protein 1A (NKR-P1A) in the rat, which is C 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu
502Lise Kveberg et al. Eur. J. Immunol. 2015. 45: 501-...