Impaired natural killer cell self-education and “missing-self” responses in Ly49-deficient mice

Abstract

Ly49-mediated recognition of MHC-I molecules on host cells is considered vital for natural killer (NK)–cell regulation and education; however, gene-deficient animal models are lacking because of the difficulty in deleting this large multigene family. Here, we describe NK gene complex knockdown (NKCKD) mice that lack expression of Ly49 and related MHC-I receptors on most NK cells. NKCKD NK cells exhibit defective killing of MHC-I–deficient, but otherwise normal, target cells, resulting in defective rejection by NKCKD mice of transplants from various types of MHC-I–deficient mice. Self–MHC-I immunosurveillance by NK cells in NKCKD mice can be rescued by self–MHC-I–specific Ly49 transgenes. Although NKCKD mice display defective recognition of MHC-I–deficient tumor cells, resulting in decreased in vivo tumor cell clearance, NKG2D- or antibody-dependent cell-mediated cytotoxicity–induced tumor cell cytotoxicity and cytokine production induced by activation receptors was efficient in Ly49-deficient NK cells, suggesting MHC-I education of NK cells is a single facet regulating their total potential. These results provide direct genetic evidence that Ly49 expression is necessary for NK-cell education to self–MHC-I molecules and that the absence of these receptors leads to loss of MHC-I–dependent “missing-self” immunosurveillance by NK cells.

Retuning of Mouse NK Cells after Interference with MHC Class I Sensing Adjusts Self-Tolerance but Preserves Anticancer Response

“…Next, we tested if the maintained missing-self killing of tumor cells after blockade of inhibitory receptors could be extended to other tumor models than RMA/RMA-S. For this purpose, we used the NKT lymphoma cell line C1498, from which an MHC I À variant was recently generated (30). The parental C1498 cells have been shown to be more efficiently rejected upon 5E6 F(ab 0 ) 2 treatment (7).…”

“…Alternatively, in the case of transfer experiments, the relative survival of target cells is given as a ratio of MHC I À versus MHC I þ inoculated cells. In vivo killing of C1498 À NKT cell lymphoma cells was performed as described by Belanger and colleagues (30), with small changes. Tumor cells were mixed with NK1.1-depleted, BMQC-labeled (10 mmol/L; Invitrogen Molecular Probes) spleen cells of impaired missing self-recognition (IMSR) mice (32) as a reference cell population, and coinjected i.p.…”

Optimized Tetramer Analysis Reveals Ly49 Promiscuity for MHC Ligands

“…Paradoxically, NK cell licensing and functional potential depend on the expression of self-MHC-I receptors during development (12,13). In agreement with these education models, the absence of Ly49 expression by NK cells in gene-targeted mice results in lack of self-MHC-I education and the loss of the ability to kill MHC-I-deficient cells (14).…”

“…We were unable to detect any difference in IFN-g production upon stimulation of Ly49G 129 -positive versus -negative NK cells, although we show in the present study that Ly49G 129 can bind to H-2D b . It is possible that the lack of licensing of Ly49G 129 seen previously is due to H-2D b being a weak self-educator as shown in splenocyte rejection assays using H-2K b2/2 , H-2D b2/2 , or H-2K b2/2 H-2D b2/2 mice as donors (14,29). Furthermore, this hypothesis agrees with the observations that Ly49A can bind to H-2D b when the L chain is of mouse origin (24), but that Ly49A + NK cell subsets in H-2 b background mice produce little if any IFN-g upon stimulation, compared with Ly49A + subsets in H-2 d background mice (30); H-2D d is a strong ligand for Ly49A (31).…”

“…DCs were isolated from collagenase (Roche Diagnostics, Laval, QC, Canada)-treated splenocytes using anti-CD11c-conjugated microbeads (Miltenyi Biotec, Auburn, CA). MHC-I-deficient C1498 cells are a derivative of the C1498 acute myeloid leukemia cells of B6 origin and were previously produced in our laboratory (14).…”