CD16− natural killer cells: enrichment in mucosal and secondary lymphoid tissues and altered function during chronic SIV infection

Abstract

Natural killer (NK) cells contribute to control of HIV/SIV infection. We defined macaque NK-cell subsets based on expression of CD56 and CD16 and found their distribution to be highly disparate. CD16 ؉ NK cells predominated in peripheral blood, whereas most mucosal NK cells were CD56 ؉ , and lymph nodes contained both CD56 ؉ and CD16 ؊ CD56 ؊ (doublenegative [DN]) subsets. Functional profiles were also distinct among subsets-CD16 ؉ NK cells expressed high levels of cytolytic molecules, and CD56 ؉ NK cells were predominantly cytokine-secreting cells, whereas DN NK possessed both functions. In macaques chronically infected with SIV, circulating CD16 ؉ and DN NK cells were expanded in number and, although markers of cytoxicity increased, cytokine secretion decreased. Notably, CD56 ؉ NK cells in SIV-infected animals up-regulated perforin, granzyme B, and CD107a. In contrast, the lymph nodehoming molecules CD62 ligand (CD62L) and C-C chemokine receptor type 7 (CCR7), which are expressed primarily on CD56 ؉ and DN NK cells, were significantly down-regulated on NK cells from infected animals. These data demonstrate that SIV infection drives a shift in NK-cell function characterized by decreased cytokine production, expanded cytotoxicity, and trafficking away from secondary lymphoid organs, suggesting that the NK-cell repertoire is not only heterogeneous but also plastic. IntroductionSince their discovery in the 1970s, natural killer (NK) cells have been considered the major effector cells of the innate immune system because of their ability to kill virus-infected or neoplastic cells. Although NK cell-mediated killing does not require prior antigen sensitization, cell-to-cell contact between NK and target T cells occurs through a complex array of inhibitory and activating receptors. In humans, NK cells express both killer-cell immunoglobulin-like receptors (KIRs), which interact with major histocompatibility complex (MHC) class I molecules and can be either inhibitory or activating, and receptors belonging to the C-type lectin family such as natural killer group 2A (NKG2A), an inhibitory receptor that recognizes HLA-E and NKG2D, which recognizes the stress-induced ligands MHC class I chain-related gene A and B (MICA/MICB) and members of the ULBP family. 1 Human NK cells also express various natural cytotoxicity receptors including NKp46, NKp30, and NKp44, for which the ligands remain incompletely characterized. 2,3 However, increasing evidence suggests that the complexity of NK-cell function has been underappreciated and that in addition to cytolysis of aberrant T cells, NK cells also produce a wide array of cytokines, mediate tolerance to self-antigens, and regulate dendritic cell functions. 4 Most recently, murine studies have suggested that NK cells may even display characteristics of adaptive immune responses. 5 In humans, 2 primary phenotypically defined subsets of NK cells have been described, cytolytic CD56 dim CD16 ϩ and cytokinesecreting CD56 bright CD16 Ϫ subsets, of which the CD56 dim CD16 ϩ subset predomina...

Gut inflammation and indoleamine deoxygenase inhibit IL-17 production and promote cytotoxic potential in NKp44+ mucosal NK cells during SIV infection

“…In contrast, NKp44 ϩ NK cells expressed very little CD56 and were negative for CD16. Furthermore, NKp46 and CD8␣, 2 molecules often used to delineate NK cells in macaques, 5,29 were expressed at high levels on NKG2A ϩ NK cells but were dimly expressed on NKp44 ϩ NK cells ( Figure 1C). We also found greater levels of the chemokine receptor CCR6 on NKp44 ϩ NK cells compared with NKG2A ϩ NK cells, whereas CXCR3 was expressed at higher levels on NKG2A ϩ NK cells, similar to published reports for human NK cells.…”

“…Next, we further evaluated the functionality of NKG2A ϩ and NKp44 ϩ NK cells in a 4-function ICS assay adapted from previous assays optimized in our laboratory. 5 After mitogen stimulation, NKp44 ϩ NK cells secreted the regulatory cytokines IL-17 and TNF-␣ but little IFN-␥, and they expressed only low levels of the degranulation marker CD107a ( Figure 1F). In strong contrast, on stimulation NKG2A ϩ NK cells secreted no IL-17, significant amounts of IFN-␥, and up-regulated CD107a.…”

“…5,25 In brief, total peripheral blood mononuclear cells were isolated from EDTA-treated venous blood by density gradient centrifugation over lymphocyte separation media (MP Biomedicals), and a hypotonic ammonium chloride solution was used to lyse contaminating red blood cells. For biopsy collection, macaques were first anesthetized with ketamine HCl (10-20 mg/kg i.m.)…”

“…To this end, we and others have recently reported a systemic but heterogeneous distribution of NK cells throughout the gastrointestinal tract as well as vagina and cervical tissues of humans and nonhuman primates. [3][4][5] Tissue NKcell subsets, like their peripheral blood counterparts, are functional, lyse the classic NK target cell line K562, express granzymes and perforin, and secrete of IFN-␥ and TNF-␣. However, recently a lymphocyte population expressing NK markers but also secreting IL-22 and IL-17, cytokines generally associated with TH17 cells, 6 was identified in human tonsillar tissue and murine lamina propria.…”

Type 3 innate lymphoid cell depletion is mediated by TLRs in lymphoid tissues of simian immunodeficiency virus‐infected macaques

“…Abbreviations: AhR, aryl hydrocarbon receptor; GALT, gutassociated lymphoid tissue; ILC, innate lymphoid cell; LTA, lipoteichoic acid; SIV, simian immunodeficiency virus; T h , T helper We and others have previously shown that CD3 2 CD8 high lymphocytes in the intestine represent a heterogeneous population including NK cells and other ILCs (2,23,24). In this study, we found that ILC3 subsets, defined by c-Kit + IL-7a + lineage-negative cells, are distinct from CD3 2 CD8 high cells, as indicated by ILC3 containing considerable CD3 2 CD8 2 cells (;70%) in macaques.…”