A Novel NKR-P1Bbright NK Cell Subset Expresses an Activated CD25+CX3CR1+CD62L−CD11b−CD27− Phenotype and Is Prevalent in Blood, Liver, and Gut-Associated Lymphoid Organs of Rats

Abstract

The inhibitory NKR-P1B receptor identifies a subset of rat splenic NK cells that is low in Ly49 receptors but enriched for CD94/NKG2 receptors. We report in this study a novel NKR-P1Bbright NK subpopulation that is prevalent in peripheral blood, liver, and gut-associated lymphoid organs and scarce in the spleen, peripheral lymph nodes, bone marrow, and lungs. This NKR-P1Bbright NK subset displays an activated phenotype, expressing CD25, CD93, CX3CR1 and near absence of CD62-L, CD11b, and CD27. Functionally, NKR-P1Bbright NK cells are highly responsive in terms of IFN-γ production and exert potent cytolytic activity. They show little spontaneous proliferation, are reduced in numbers upon in vivo activation with polyinosinic:polycytidylic acid, and have poor survival in ex vivo cytokine cultures. Our findings suggest that NKR-P1Bbright NK cells are fully differentiated effector cells that rapidly die upon further activation. The identification of this novel rat NK cell subset may facilitate future translational research of the role of distinct NK cell subsets under normal physiological conditions and during ongoing immune responses.