o:1762 The Natural Cytotoxicity Receptor NKp44 (NCR2, CD336) Is Expressed on the Majority of Porcine NK Cells Ex Vivo Without Stimulation en Natural killer (NK) cells have been studied extensively in humans and mice for their vital role in the vertebrate innate immune system. They are known to rapidly eliminate tumors or virus infected cells in an immune response utilizing their lytic properties. The natural cytotoxicity receptors (NCRs) NKp30 (NCR3), NKp44 (NCR2), and NKp46 (NCR1) are important mediators of NK-cell cytotoxicity. NKp44 expression was reported for NK cells in humans as well as in some non-human primates and found exclusively on activated NK cells. Previously, no information was available on NKp44 protein expression and its role in porcine lymphocytes due to the lack of species-specific monoclonal antibodies (mAbs). For this study, porcine-specific anti-NKp44 mAbs were generated and their reactivity was tested on blood and tissue derived NK cells in pigs of different age classes. Interestingly, NKp44 expression was detected ex vivo already on resting NK cells; moreover, the frequency of NKp44+ NK cells was higher than that of NKp46+ NK cells in most animals analyzed. Upon in vitro stimulation with IL-2 or IL-15, the frequency of NKp44+ NK cells, as well as the intensity of NKp44 expression at the single cell level, were increased. Since little is known about swine NK cells, the generation of a mAb (clone 54-1) against NKp44 will greatly aid in elucidating the mechanisms underlying the differentiation, functionality, and activation of porcine NK cells. Killer-Cells; Monoclonal-Antibodies; Activation; Recognition; Infection; Subsets; Nkp30; Pigs; Ige 1552099 10.3389/fimmu.2022.767530 2023-06-27T11:40:05.060Z 44 yes 46 Kerstin H. Mair University of Veterinary Medicine Vienna Joan K. Lunney United States Department of Agriculture person Armin Saalmüller University of Veterinary Medicine Vienna person 0000-0002-7703-3252 Wilhelm Gerner University of Veterinary Medicine Vienna / The Pirbright Institute person 0000-0002-2431-5889 Katinka A van Dongen University of Veterinary Medicine Vienna person Maria Stadler University of Veterinary Medicine Vienna person Dante Zarlenga United States Department of Agriculture person Patricia Boyd United States Department of Agriculture person Leela Noronha Cornell University / United States Department of Agriculture person Susanna Babasyan Cornell University person Bettina Wagner Cornell University person Assiatu J. Crossman National Institutes of Health / United States Department of Agriculture person application/pdf 6382478 https://phaidra.vetmeduni.ac.at/o:1762 no yes 16 70 1552253 Frontiers in Immunology 15 13 Frontiers Media Sa 2022