Circulating Human Collagen II-Reactive T Cell in Early Rheumatoid Arthritis Produce IL17.

Background/Purpose: Joint damage in Rheumatoid Arthritis is likely due to pro-inflammatory T cells specific for collagen and recruited into the synovium, where they are activated and promote acute presentation of the disease. We previously described the T cell repertoire specific for human Collagen II peptide 261–273 (huColl261) in HLA-DR4_ Early Rheumatoid Arthritis (ERA) patients, compared to that of DR4_ healthy subjects and followed it along disease course, showing that T cells specific for this epitope appear during flares of the disease but tend to disappear during remission (Ria et al., Art Res Ther, 2008). Here we report preliminary observations regarding the presence of specific clonotypes recognized by the ability of hColl-specific (HuColl2) T cells to respond to Collagen II peptide and we describe that they seem to secrete IL-17 more than IL-13. Methods: PBMC obtained from 22 consecutive ERA patients were collected. All patients were typed for HLA-DRB1. 11 patients were DR 4+, 4 were DR1+ one was DR 4,1+. Patients were tested for the presence of HuColl2 peptide response by immunoscope. In 4 ERA patients synovial fluid cells were also examined. PBMC were also purified from 2 ERA patients and one RA patient at his first remission of disease, and stimulated in vitro with huColl261. Sixteen hours later, IL-17 and IL-13 secreting cells were enriched by MACS® secretion assay. The presence of huColl261-specific TCRs was assessed by immunoscope in samples enriched or depleted for each cytokine, and in samples allowed to proliferate for 3 days in response to the peptide antigen. Results: We examined the usage of two TCR beta chains that we showed to be frequently used in DR4+ ERA patients. Collagen-specific T cells carrying BV11(139b) were used by 6/12 ERA DR4+ subjects, 2/4 DR1+ subjects (that were both also DR15+) and by 2/6 patients negative for both DR4 and DR1. Usage of BV13b (199) appears to be more specific for DR4+ subjects, since we found collagen specific T cells using this TCR-beta chain in 5/10 DR4+ ERA patients versus 1/10 DR4- ERA subjects. T cells obtained from 3 PB samples were tested for their capacity to secrete specific cytokines (IL17 or IL13) in response to stimulation with collagen II. T cells secreting any of the two cytokine represent only a part of the circulating T cell repertoire specific for huColl261, similar to the observation that a minority of the circulating repertoire is actually able to home to the synovium. IL17-secreting cells were detected in all 3 samples, but it appears that T cells from one patient in remission needed additional stimuli that include bacterial derived non antigenic moieties in order to produce IL-17. huColl261-specific IL-13 producing cells were detected only in one of the 2 ERA subjects. Conclusion: By the immunoscope technique we could dissect the immune response against human collagen in ERA subjects. Results show that some rearrangements of the TCR-beta chain co-segregate with the collagenspecific response restricted by DR4 and/or DR1. The T cell precursors actually driving the proinflammatory response in the synovium by the production of IL-17 appears to represent a limited portion of the entire collagen specific repertoire.