Three common alleles of KIR2DL4 (CD158d) encode constitutively expressed, inducible and secreted receptors in NK cells

Abstract

Genetic polymorphism of KIR2DL4 results in alleles with either 9 or 10 consecutive adenines in exon 6, which encodes the transmembrane domain. "10A" alleles encode a membrane-expressed receptor that is constitutively expressed on resting CD56bright NK cells and on CD56 dim cells after culture. However, in some individuals with the 10A allele, KIR2DL4 cannot be detected on their resting CD56 bright NK cells. "9A" alleles have been predicted to encode a secreted receptor due to the splicing out of the transmembrane region. In this publication, we show that those individuals with a 10A allele who lack detectable KIR2DL4 on CD56 bright NK cells express a KIR2DL4 receptor in which the D0-domain is excised. This D-D0 receptor cannot be detected by the available anti-KIR2DL4 monoclonal antibodies. In such individuals, KIR2DL4 becomes detectable on cultured NK cells due to up-regulation of the full-length KIR2DL4 transcript. In all individuals with 10A alleles, KIR2DL4 ceases to be expressed at the cell surface 16 days after activation, despite the maintenance of maximal levels of KIR2DL4 mRNA transcription, suggesting the existence of a negative regulator of cell surface expression. Finally, we show that the 9A allele can produce a secreted KIR2DL4 receptor.

Phenotypic and Functional Analyses of KIR3DL1+ and KIR3DS1+ NK Cell Subsets Demonstrate Differential Regulation by Bw4 Molecules and Induced KIR3DS1 Expression on Stimulated NK Cells

“…The induction of KIR expression on NK cells is poorly described in literature. Certain allelic variants of KIR2DL4 have been shown to be induced on cultured NK cells, either as a full-length and detectable protein, or as a secreted receptor (45). A higher KIR3DS1 expression on NK cells has been observed in vivo in the context of HIV infection (34).…”

Deciphering the killer‐cell immunoglobulin‐like receptor system at super‐resolution for natural killer and T‐cell biology

“…3). Even a single nucleotide mutation can dramatically change receptor expression,25, 31, 32, 33 ligand specificity34, 35, 36 or signalling strength. KIR gene copy number variation influences NK cell education, shaping the NK cell repertoire 37.…”

Killer Ig-like Receptor 2DL4 Does Not Mediate NK Cell IFN-γ Responses to Soluble HLA-G Preparations

“…Freshly isolated NK cells, but not cultured NK cells, produce IFN-g in response to sHLA-G We have previously shown that plate-bound anti-KIR2DL4 mAb stimulates IFN-g production from 14-d IL-2-cultured NK cells from donors with at least one KIR2DL4 10A-A allele, which encodes a membrane-expressed receptor (10). In view of reports that soluble anti-KIR2DL4 stimulates IFN-g from freshly isolated NK cells, we tested the ability of three different soluble anti-KIR2DL4 mAbs to stimulate IFN-g in 14-d cultured NK cells.…”

“…Additional Abs in the EasySep kit were CD20, CD14, HLA-DR, and CD123. Purified NK cells were incubated with freshly irradiated Daudi feeder cells and 200 IU/ml rIL-2 (T3267; Sigma, St. Louis, MO) as described previously (10).…”

“…All other KIRs are expressed constitutively on a subset of CD56 dim NK cells (6,7), whereas KIR2DL4 is primarily expressed on CD56 bright NK cells, although its expression on all NK cells can be induced by culture with IL-2 (8,9). However, membrane expression of KIR2DL4 occurs only at low density and only in individuals with at least one copy of the 10A-A TM (-TM) allele, and not in individuals homozygous for the common 9A-DTM and 10A-B alleles (9,10). The 10A-A, 10A-B, and 9A-DTM alleles all occur at frequencies .20% (11,12), suggesting balancing selection between the alleles, the cause of which is yet to be determined.…”