Abnormal T cell differentiation persists in patients with rheumatoid arthritis in clinical remission and predicts relapse C H Burgoyne, 1,2 S L Field, 1,2 A K Brown, 1,2 E M Hensor, 3 A English, 1,2 S L Bingham, 1,2 R Verburg, 4 U Fearon, 1,2 C A Lawson, 1,2 P J Hamlin, 5 L Straszynski, 2 D Veale, 1,2 P Conaghan, 1,2 M A Hull, 2,5 J M van Laar, 4 A Tennant, 3 P Emery, 1,2 J D Isaacs, 1,2 F Ponchel 1,2 1 Academic Unit of Musculoskeletal Disease, University of Leeds, Leeds, UK; 2 Leeds Institute of Molecular Medicine, University of Leeds, Leeds, UK; 3 Psychometric Laboratory, University of Leeds, Leeds, UK; 4 Rheumatology Department, Leiden University Medical Center, Leiden, The Netherlands; 5 Centre for Digestive Diseases, Leeds General Infirmary, Leeds, UK Correspondence to: Dr Frederique Ponchel, Leeds Institute of Molecular Medicine, Clinical Sciences Building, St James’s University Hospital, Leeds, LS9 7TF, UK; F.Ponchel@leeds.ac.uk Accepted 5 July 2007 Published Online First 20 July 2007 ABSTRACT Objectives: An abnormal CD4+ T cell subset related to inflammation exposure (inflammation-related cells, IRC) has been identified in rheumatoid arthritis (RA). Patients with inflammatory and non-inflammatory diseases were used to examine the relationship between inflammation and this T cell subset in vivo. Methods: Blood was collected from healthy controls and patients with RA (active disease or in clinical remission), Crohn’s disease and osteoarthritis. IRC and chemokine receptors were quantified by flow cytometry. Thymic activity and apoptotic factors were measured by real-time polymerase chain reaction. Circulating cytokines were measured by enzyme-linked immunosorbent assay. CXCR4 and SDF1 in synovial biopsies were measured using immunohistochemistry. Results: IRC were identified in patients with RA (p,0.0001) and Crohn’s disease (p = 0.005), but not in those with osteoarthritis. In RA in remission, IRC persisted (p,0.001). In remission, hyperproliferation of IRC was lost, chemokine receptor expression was significantly lowered (p,0.007), Bax expression dropped significantly (p,0.001) and was inversely correlated with IRC (rho = 20.755, p = 0.03). High IRC frequency in remis- sion was associated with relapse within 18 months (OR = 6.4, p,0.001) and a regression model predicted 72% of relapse. Conclusions: These results suggest a model in which, despite the lack of systemic inflammation, IRC persist in remission, indicating that IRC are an acquired feature of RA. They have, however, lost their hyper-responsiveness, acquired a potential for survival, and no longer express chemokine receptors. IRC persistence in remission confirms their important role in chronic inflammation as circulating precursors of pathogenic cells. This was further demonstrated by much higher incidence of relapse in patients with high IRC frequency in remission. Rheumatoid arthritis (RA) is a chronic inflamma- tory disease of joints and extra-articular tissues, which results in severe disability and premature mortality. 1 The exact pathogenesis of RA remains uncertain; however, autoimmune processes are evidenced by major histocompatibility complex linkage, 23 autoantibody production and lympho- cyte infiltration of the synovial tissue. 4 All of these features support the hypothesis of a T cell driven disease, 5–7 although this ‘‘T centric’’ paradigm has been challenged. 89 We recently proposed a model of T cell differ- entiation and demonstrated divergences in relation to chronic inflammation in RA. 10 Isoforms of the tyrosine phosphatase CD45 coupled with lymph node homing receptor CD62L expression, were used to distinguish ‘‘naı ¨ve’’ from ‘‘memory’’ T cells. Using this model, we demonstrated the presence of atypical subsets of cells in RA, expressing aberrant combinations of naı ¨ve and memory markers. 10 One subset was characterised by the cell surface expres- sion of CD45RB high CD45RA+ CD45RO low CD62L–. We named them inflammation-related cells (IRC), as the frequency of these cells in the periphery was directly correlated with systemic levels of inflam- mation measured by C-reactive protein (CRP). Retention of CD45RB and CD45RA expression by IRC, and their relatively high T cell receptor excision circle (TREC) content compared with naı ¨ve cells, suggested that they were relatively immature and we postulated that they resulted from inflamma- tion-driven differentiation and proliferation of naı ¨ve cells. 10 They were also hyper-responsive to mitogen and antigen stimulation. Cells with a similar phenotype have been described by other groups. Naı ¨ve CD4+ T cells treated with a combination of interleukin (IL)-2, IL-6 and tumour necrosis factor (TNF)-a or with IL-15 developed a phenotype similar to IRC, losing CD62L but retaining CD45RA and several other markers of activation. 11 12 Activation under similar conditions induces the expression of chemokine receptors such as CXCR4, 13 suggesting that such cells are destined to home to sites of inflammation. RA synovial T cells have been shown to share many features with cytokine-activated T cells, in particular with regard to their ability to induce macrophage production of TNF-a. 14 Our current hypothesis is that, following an initiation phase, T cells in RA are essential to the perpetuation of the disease in a non-specific way. Chronic inflammation triggers cytokine T cell activation independently of antigen. These cyto- kine-activated T cells express chemokine receptors and home to inflamed tissue, where they perpetuate the disease ultimately leading to the destruction of cartilage and bone. In the current study, we used several cohorts of patients with RA, inflammatory and non-inflammatory disease controls and healthy individuals, to study the relationship between inflammation and T cell phenotype in vivo. Extended report 750 Ann Rheum Dis 2008;67:750–757. doi:10.1136/ard.2007.073833