Bovine neonate natural killer cells are fully functional and highly responsive to interleukin-15 and to NKp46 receptor stimulationJamila Elhmouzi-Younes1, Anne K. Storset2, Preben Boysen2, Fabrice Laurent1 and Françoise Drouet1
1 INRA, UR1282, Infectiologie Animale et Santé Publique, Laboratoire Contrôle et Immunologie des Maladies Entériques du Nouveau-né, F-37380 Nouzilly, France
2 Department of Food safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., N-0033 Oslo, Norway
Received 28 January 2009; accepted 23 June 2009; published online 24 June 2009
Abstract - Natural killer (NK) cells are key components of the innate immune system with their killing and cytokine producing abilities. Bovine NK cells have been characterized as NKp46+/CD3- lymphocytes, but little is known about these cells in neonatal calves. As the newborn calf, with an insufficiently developed acquired immunity, has to employ the innate immune system, we wanted to investigate whether neonate NK cells had the same characteristics as cells from older calves. Freshly isolated neonate and calf NK cells presented the same resting CD2+/CD25 /CD8 phenotype. Neonates less than 8 days old had one third of the circulating NKp46+ cells of older calves, but the NK cells proliferated more actively in vitro in the presence of interleukin (IL)-2 or IL-15. Moreover, neonate NK cells were more cytotoxic both in an NKp46 mediated redirected lysis assay and in direct killing of a bovine cell line MDBK when cultured in the presence of IL-15. Neonate and calf NK cells cultured in the presence of IL-2 and then stimulated with IL-12 produced similar dose-dependent interferon (IFN)- amounts, while IL-15 cultured NK cells did not give such a response whatever the age. However, neonatal NK cells cultured in IL-15 and stimulated by IL-12 concomitantly with cross-linking of NKp46, produced 4 to 5 times more IFN- than calf NK cells. These data suggest that although present in lower number at birth, neonate NK cells are fully functional and are more responsive to IL-15 and activation through the NKp46 receptor than NK cells from older calves.
Key words: natural killer cell / neonate / bovine / cytotoxicity / interleukin
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© INRA, EDP Sciences 2009