CD4 helper T cells producing the pro-inflammatory cytokine IL17 (Th17) have been implicated in a number of inflammatory arthritides including the Spondyloarthritides. Th17 development is promoted by IL23. Ankylosing Spondylitis (AS), the commonest Spondyloarthritis, is genetically associated with both HLA-B27 (B27) and with IL23 receptor polymorphisms, however the link remains unexplained. We have previously shown that B27 can form heavy chain dimers (termed B272), which, unlike classical HLA-B27, bind the Killer-cell Immunoglobulin-like Receptor KIR3DL2. Here we show that B272-expressing antigen presenting cells stimulate the survival, proliferation and IL17 production of KIR3DL2+ CD4 T. KIR3DL2+ CD4 T cells are expanded and enriched for IL17 production in the blood and synovial fluid of patients with spondyloarthritis (SpA). Despite KIR3DL2+ cells comprising a mean of just 15% of CD4 T in the peripheral blood of SpA patients, this subset accounted for 70% of the observed increase in Th17 numbers in SpA subjects compared to controls. TCR-stimulated peripheral blood KIR3DL2+CD4 T cell lines from SpA patients secreted four fold more IL17 than KIR3DL2+ lines from controls or KIR3DL2-negative CD4 T. Strikingly, KIR3DL2+ CD4 T cells account for the majority of peripheral blood CD4 T cell IL23 receptor expression and produce more IL17 in the presence of IL23. Our findings link HLA-B27 with IL-17 production and suggest new therapeutic strategies in AS/SpA.

The antibodies Ki-M8, Ber-Mac3, GHI/61 and SM4 define a human macrophage-associated antigen with a relative molecular mass of 130,000 which we designate M130. The protein was purified by immunoaffinity chromatography and an N-terminal and three internal amino acid sequences were obtained. A cDNA fragment was initially obtained by polymerase chain reaction (PCR) using reverse-translated primers. Several variant cDNA clones, derived from alternative spliced messages, were obtained from a lipopolysaccharide-stimulated human monocyte library and were sequenced. The relative abundance of these variants was evaluated by a series of overlapping PCR reactions. The size of the most representative cDNA is 3.7 kb and closely agrees with the mRNA size of 3.8 kb determined by Northern blot analysis. The membrane protein encoded contains a leader peptide of 40 residues, a putative extracellular domain of 1003 residues, followed by a hydrophobic segment of 24 residues and a cytoplasmic domain of 49 residues. The extracellular domain was found to contain nine repeating elements, of about 110 residues, which are similar to those of the scavenger receptor superfamily.

The adhesive response of circulating leukocytes to inflammatory stimuli is now well documented (1, 2). After such signals, leukocytes adhere to the blood vasculature using selectin-mediated interactions, and this stage leads to activation of their integrins. The β2 or leukocyte integrins lymphocyte function-associated molecule (LFA)-1 (CD11a/CD18) has a major role in the firm adhesion of leukocytes to endothelium and in their migration across this barrier. In addition, LFA-1 cooperates with the T-cell receptor in antigen-stimulated T-cell priming (3) and, in general, participates in the formation of leukocyte-leukocyte contacts. Mac-1 (CD11b/CD18) is a major phagocytic receptor operating in association with the third β2 integrin, p150,95 (CD11c/CD18), and both recognize as ligands fibrinogen and the complement fragment iC3b (4, 5).Expression of integrins on the cell membrane is not a guarantee of their ability to function as adhesion receptors. Integrins must undergo conversion from inactive to active ligand-binding status, which occurs through a process of clustering and/or altered conformation (6, 7). The stimulus for this activation is initiated by the triggering of other membrane receptors, a route of signal transduction that has been termed "inside out" signaling. The integrins bind divalent cations such as Mg 2+ or Mn 2+ in order to function, and an alternative means of directly altering integrin activity is through extracellular exposure to these cations. It is thought that these latter procedures mimic the conformational changes brought about by integrin-activating signals generated intracellularly. Special anti-integrin monoclonal antibodies (MABs) can serve as reporters of this activation. For example, MAB 24 recognizes an epitope on high-affinity β2 integrin (7) and detects a conformational change in the form of interdomain movement involving the ligand binding I domain on the integrin α subunit (8).Valuable information about the functioning of the β2 integrins has come from study of the leukocyte adhesion deficiency (LAD)-1 syndrome. LAD-1 is an autosomal recessive disorder caused by mutation in the CD18 gene on chromosome 21 that leads to absent or aberrant biosynthesis of the β2 subunit of leukocyte integrins (9-11). This lesion is reflected in the absence or markedly diminished expression on the leukocyte cell surface of the β2 integrins, CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), and CD11c/CD18 (p150,95). The patient phenotype is variable but reflects the level of β2 integrins expressed. Patients with <1% expression suffer from life-threatening infections and require bone marrow transplantation for long-term survival (12). In patients with 1%-10% expression, defects in leukocyte mobility, adherence, and endocytosis lead to periodic periodontitis, skin infections, and retarded wound healing with dysplastic scarring. The heterozygotic relatives of the patients have ∼40%-60% normal levels of β2 inte- In the leukocyte adhesion deficiency (LAD)-1 syndrome, there is diminished expression of β2 (CD18) inte...