Original Contributions CLONING AND CHROMOSOME MAPPING OF THE HUMAN INTERLEUKIN-1 RECEPTOR ANTAGONIST GENE Andrew Lennard, Pat German,’ Martin Carrier, Samantha Griffiths, Hilary Scotney, Denise Sheer,l Roberto Solari By screening a human genomic library with an interleukin-1 receptor antagonist (IL-lra) cDNA probe, we have isolated a 15 kb clone which contains the entire coding region of the gene as expressed in monocytes, and includes 6 kb of S-upstream sequence. The gene contains four exons which code for the secreted form of the IL-lra, however, our clone does not contain the alternative first exon used to generate an intracellular form of the protein as found in epithelial cells. Analysis of the sequence reveals a consensus TATA box, and three Alu repeats, two of which are in the upstream region and one in intron 3. The sequence also reveals an 86 bp motif tandomly repeated four times within intron 2, and may reflect the polymorphism known to exist in this region of the gene. By in-situ fluorescence hybridization we have shown that the IL- lra gene is found on the long arm of chromosome 2 and maps to 2q13-14.1. Previous studies have revealed that IL-la, IL-li3 and both type I and type II forms of the IL-1 receptor all map close to this region of chromosome 2. The increasingly complex cytokine network involves both positive and negative regulatory pathways. Natural inhibitors of cytokine function are of great importance both as analytical tools and as potential therapeutic agents. These inhibitors include soluble extracellular domains of cytokine receptors that may arise by proteolytic cleavage, as in the case of tumour necrosis factor (TNF) receptors,’ or as alternatively spliced transcripts of the functional transmembrane receptor as in the case of IL-42 and IL-7: receptors. Another class of inhibitor are true cytokine receptor antagonists, the best characterized of which is theinterleukin-1 receptor antagonist (IL- From the Yamanouchi Research Institute UK, Littlemore Hospital, Oxford OX4 4XN; and Human Cytogenetics Laboratory, Imperial Cancer Research Fund, P.O. Box 123, Lincoln’s Inn Fields, London WC2A 3PX.’ Address correspondence to: Andrew Lennard. Received 16 December 1991; accepted for publication 7 January 1992. 0 1992 Academic Press Limited 1043-4666/92/020083+07 $0500/O KEY WORDS: IL-lra/IL-1 receptor antagonist/interleukin/ genomic sequence CYTOKINE, Vol. 4, No. 2 (March); 1992: pp 83-89 lra). The IL-lra protein was first purified and characterized from human monocyte conditioned medium and the corresponding cDNA subsequently cloned.@ The IL-lra produced by monocytes is a secreted protein structurally related to IL-la and IL-ll3 that forms a non-productive complex with the IL-l receptor (IL-1R). Although Il-lra activity was first characterized from monocytes, it is also expressed in neutrophils and epithelial cells7 Interestingly, epithelial cell IL-lra is expressed as an alternatively spliced transcript of the monocyte IL-lra which lacks a leader peptide and consequently is not secreted from the cell. Both IL-l and IL-lra bind to the type I and type II IL-l receptors with comparable affinities&l1 and therefore the receptor antagonist is an effective inhibitor of IL-l induced effects. Indeed a large number of cases have now been reported in which recombinant IL-lra has been used both in vitro and in vivo to block a range of IL-l-induced biological activities.12 However the precise physiological relationship between IL-l and IL-lra production in normal and pathological processes is as yet poorly understood. Since monocytes synthesize both IL-l and the IL-lra, the pro-inflammatory effects of IL-l may, in 83