The Journal of Immunology Killer Cell Ig-Like Receptor and Leukocyte Ig-Like Receptor Transgenic Mice Exhibit Tissue- and Cell-Specific Transgene Expression1 Danny Belkin,* Michaela Torkar,* Chiwen Chang,* Roland Barten,* Mauro Tolaini,† Anja Haude,* Rachel Allen,* Michael J. Wilson,* Dimitris Kioussis,† and John Trowsdale2* To generate an experimental model for exploring the function, expression pattern, and developmental regulation of human Ig-like activating and inhibitory receptors, we have generated transgenic mice using two human genomic clones: 52N12 (a 150-Kb clone encompassing the leukocyte Ig-like receptor (LILR)B1 (ILT2), LILRB4 (ILT3), and LILRA1 (LIR6) genes) and 1060P11 (a 160-Kb clone that contains ten killer cell Ig-like receptor (KIR) genes). Both the KIR and LILR families are encoded within the leukocyte receptor complex, and are involved in immune modulation. We have also produced a novel mAb to LILRA1 to facilitate expression studies. The LILR transgenes were expressed in a similar, but not identical, pattern to that observed in humans: LILRB1 was expressed in B cells, most NK cells, and a small number of T cells; LILRB4 was expressed in a B cell subset; and LILRA1 was found on a ring of cells surrounding B cell areas on spleen sections, consistent with other data showing monocyte/macrophage expression. KIR transgenic mice showed KIR2DL2 expression on a subset of NK cells and T cells, similar to the pattern seen in humans, and expression of KIR2DL4, KIR3DS1, and KIR2DL5 by splenic NK cells. These observations indicate that linked regulatory elements within the genomic clones are sufficient to allow appropriate expression of KIRs in mice, and illustrate that the presence of the natural ligands for these receptors, in the form of human MHC class I proteins, is not necessary for the expression of the KIRs observed in these mice. The Journal of Immunology, 2003, 171: 3056–3063. atural killer cells are involved in immune responses to transmembrane domain. Associated transmembrane adapter pro- tumor cells and to viral, bacterial, and parasitic infec- teins carry an immunotyrosine-based activation motif for signal N tions (1, 2). Attack by NK cells is regulated by a com- transduction. Inhibitory type KIR and LILR, characterized by a bination of signals from inhibitory and stimulatory receptors on the long cytoplasmic tail-bearing immunotyrosine-based inhibitory cell surface. MHC class I-specific inhibitory receptors are the best motif, have been shown to inhibit cell activation of monocytes, B understood of these and include members of the human killer cell cells, NK cells, and T cells (8–11). 3 Ig-like receptor (KIR) family, their functional homologues the Different KIR gene products can be detected on overlapping sets murine Ly49 family, and the NKG2/CD94 receptors (present in of human NK cells (12, 13). Each NK clone expresses at least one both species) (3, 4). Additional immune receptors such as the leu- inhibitory receptor. Variegated patterns of expression suggest a kocyte Ig-like receptors (LILR, also known as Ig-like transcripts stochastic mechanism of KIR expression (14). KIR expression is (ILT), LIR, or CD85), and the murine paired Ig-like receptors are likely to be controlled by highly homologous upstream promoter closely related to KIRs in structure and presumably also in func- sequences (with the exception of KIR2DL4, which possesses a tion. Both KIRs and LILRs are encoded within the leukocyte re- more divergent promoter and is constitutively expressed in all NK ceptor complex (LRC) on human chromosome 19q13.42, a region clones) (5). It has been demonstrated that the frequency with which of the genome that exhibits marked inter- and intraspecies varia- cells express a combination of Ly49 receptors is a product of their tion (5–7). individual frequencies, leading to the proposal of the “product KIR and LILR receptors are members of the Ig superfamily and rule” (15). Higher-order, chromatin-related regulation also seems exist in both activating and inhibitory isoforms. The activating to be involved, as there appears to be a correlation between meth- type, characterized by a short cytoplasmic tail, associate with ylation upstream of the transcriptional start site and reduced KIR adapter proteins via a positively charged arginine residue in their expression (16). MHC class I molecules also exert an effect on the repertoire of NK receptor expression. An example of this was seen *Immunology Division, Department of Pathology, University of Cambridge, Cam- in MHC class I-deficient mice, which showed higher frequencies † bridge, United Kingdom; and Division of Molecular Immunology, National Institute of NK cells coexpressing different inhibitory Ly49 receptors when for Medical Research, London, United Kingdom compared with normal mice, indicating that the interaction of Ly49 Received for publication November 20, 2002. Accepted for publication July 3, 2003. receptors with their MHC class I ligands shape the receptor rep- The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance ertoire by limiting receptor coexpression (17, 18). This effect is with 18 U.S.C. Section 1734 solely to indicate this fact. consistent with a sequential regulated expression model, which 1 This work was supported by the Wellcome Trust and the Medical Research Council. proposes that the MHC reactivity of receptors expressed early 2 Address correspondence and reprint requests to Dr. John Trowsdale, Immunology in the sequence determines whether other receptors will be sub- Division, Department of Pathology, University of Cambridge, Tennis Court Road, sequently expressed. This happens to the extent that even MHC Cambridge CB2 1QP, U.K. E-mail address: [email protected] haplotypes, which did not detectably bind certain Ly49 recep- 3 Abbreviations used in this paper: KIR, killer cell Ig-like receptor; LILR, leukocyte Ig-like receptor; FISH, fluorescence in situ hybridization; LRC, leukocyte receptor tors, impacted coexpression of these receptors with other Ly49 complex; PAC, P1 artificial chromosome. molecules (15, 17–20). Copyright © 2003 by The American Association of Immunologists, Inc. 0022-1767/03/$02.00 The Journal of Immunology 3057 Many LILR-related sequences have been described to date. be addressed. Previous work generated KIR2DL3 transgenic mice, Most are transmembrane glycoproteins with an extracellular, li- and used them to investigate KIR function and the possible affects gand-binding region composed of either two or four Ig domains. the ligand for this KIR, HLA-Cw3, exerts on KIR expression (32). LILR-mediated immune modulation may affect cells of both the This study showed that KIRs can be expressed without the need innate and adaptive immune systems. LILRB1 (ILT2/LIR1) shows for the presence of their cognate human ligands, MHC class I. an exceptionally wide expression pattern and can be found on the The use of the H-2kb promoter in this transgene conferred an ϩ majority of CD14 myelomonocytic cells and B cells in addition expression pattern that differed markedly from the one observed to NK and T cell subsets (21, 22). LILRA2 (ILT1/LIR7) and in humans. LILRB3 (ILT5/LIR3) are expressed by myeloid cells, granulo- In this study we describe the generation of two lines of LILR trans- cytes, and subsets of NK or T cells (21, 23), while LILRB4 (ILT3/ genic mice, and one line of KIR transgenic mice, using genomic con- LIR5) is expressed only on myeloid cells (8). cDNA studies indi- structs from the LRC. Official KIR and LILR nomenclature is de- cate that LILRB5 (LIR8) may be the only NK cell specific LILR scribed at http://www.gene.ucl.ac.uk/nomenclature/genefamily.shtml. (24). ILT7, ILT8 and LILRA1 (LIR6) are expressed in monocytes but not on B, T, or NK cells (24, 25). Little is known about the Materials and Methods control of LILR gene expression, although there is preliminary Transgene production evidence that some LILRs show similar clonotypic expression pat- terns to KIRs (21). The P1 artificial chromosome (PAC) clones 1060P11 and 52N12 (con- structed using the vector pCYPAC2 in the Escherichia coli host strain The ligands that have been identified for LILRB1, LILRB2 DH10B) were used for the creation of transgenic mice (Fig. 1) (33). For (ILT4/LIR2), and LILRA1 are all HLA class I molecules. LILRB1 large scale, genomic DNA-free purification of PAC DNA, cesium chloride and LILRB2 recognize classical, nonclassical, and viral ortho- gradients and a Qiagen Large Construct kit (Valencia, CA) were used. The logues of HLA class I (10, 21, 22, 26). LILRB2 can also recognize microinjection fragments were isolated from the vector by restriction with free H chain forms of HLA class I. LILRA1 has been shown to the restriction enzymes NgoMIV and NotI followed by centrifugation through a 10–25% sodium chloride gradient. Fractions were collected and recognize HLA B27 but does not recognize the nonclassical analyzed by pulse field gel electrophoresis to assess for purity of insert HLA-F protein (27) (R. L. Allen and E. Lepin, unpublished ob- from both vector and E. coli DNA. servations), so it appears to have more restricted specificity. Insert DNA was diluted, precipitated with ethanol, then resuspended ϫ Activation of monocytes through receptors such as Fc␥RIII and twice in 0.25 Tris-taurin-EDTA. Before microinjection, DNA was passed ␥ through an Elutip minicolumn (Schleicher and Scheull, Keene, NH) fol- Fc RII can be inhibited by coligation of inhibitory LILR (8, 10). lowing the manufacturer’s instructions. Eluted DNA was precipitated with The inhibitory process is mediated by Src homology 2-containing ethanol then resuspended in 10 mM Tris-HCl, 2 mM EDTA, pH7.4 at a phosphatases 1 and 2 (28). Activating LILRs use a similar signal- concentration of 5–10 ␮g/ml and then microinjected (43). ing mechanism to the Fc␣R.