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The IL-1 receptor antagonist (IL-1RN) is a protein that binds to IL-1 receptors and inhibits the binding of IL-1 alpha and IL-1 beta. As a consequence, the biological activity of these two cytokines is neutralized in physiological and pathophysiological immune and inflammatory responses. In this study, using a panel of somatic rodent-human cell hybrids, we show that the gene for the human interleukin-1 receptor antagonist (IL1RN) maps to the long arm of chromosome 2. Previously, we described a length variation polymorphism within the second intron of the IL-1RN gene (Steinkasserer et al., 1991, Nucleic Acids Res. 19: 5095). Segregation of this, together with an IL-1 alpha polymorphism, was followed in a panel of five CEPH families. Linkage analysis permitted the mapping of the IL-1RN gene to band q14-q21 in the region for the IL-1 alpha and IL-1 beta loci. This study supports the view that an early gene duplication event resulted in the creation of an interleukin-1 gene family.

Human apolipoprotein H (APOH) is associated with lipoprotein present in plasma. It has been shown that APOH has structural similarities with the regulation of complement activation (RCA) protein superfamily and is involved in phospholipid binding interactions on platelets and as an autoantigen in complex with anionic phospholipids. Nevertheless, additional functional studies are necessary to establish the physiological role of APOH. By hybridizing a cDNA probe for APOH to a panel of somatic cell hybrids, we show that the structural locus for this protein maps to 17q23----qter and is therefore not part of the RCA cluster on chromosome 1. The site of biosynthesis for APOH was established by Northern blot analysis. Hybridization of the APOH cDNA probe to total liver RNA identified a transcript of approximately 1.5 kb.

The nucleotide and complete amino acid sequence for the human beta 2-glycoprotein I (beta 2I) was derived by sequencing the cDNA clone pB2I-1. In addition to the 326 amino acid residues of the mature protein this clone codes for a putative leader peptide and contains sequence representing 5' and 3' untranslated regions. When this amino acid sequence was compared with the previously published primary sequence, three major amino acid substitutions were found, two involving cysteine residues. These substitutions lead to a new alignment of the complement control protein (CCP) repeats present in beta 2I and a prediction of the complete disulphide bond organization. Northern-blot analysis indicates that hepatocytes are a major site of biosynthesis for this protein. A transcription signal of about 1.5 kb was detected by using RNA from HepG2 cells.