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Background/Aims The role of highly differentiated T effector memory re-expressing CD45RA (Temra) in rheumatoid arthritis (RA) is unclear, including whether they can be used as a marker of persistent disease activity. Our aim was to investigate whether peripheral blood Temra frequency can be used to identify RA patients with active disease refractory to anti-TNF therapy. As cytomegalovirus (CMV) has been reported to be associated with the expansion of Temra as well as implicated in RA pathogenesis, we also explored the relationship between serum CMV immunoglobulin (IgG) status, Temra, and remission status. Methods A cross-sectional cohort of RA patients on anti-TNF therapy were recruited. Patients were stratified based on remission status. Remission was defined as no recorded DAS28-CRP≥2.4, no swollen joints, no C-reactive protein (CRP) >5mg/L, and on a stable DMARD dose and no reported disease flare/loss of remission in the last 6 months before recruitment. Patients on abatacept or on conventional DMARDs only were recruited as comparison groups. Peripheral blood mononuclear cells (PBMC) were analysed by flow cytometry. Serum CMV IgG was analysed by ELISA. Two-tailed Mann-Whitney U test or unpaired t-test were used to obtain unadjusted values, analysis of variance (ANOVA) of log-transformed data to obtain age-adjusted values, Spearman’s rank correlation to compare correlation between two variables, Fisher’s exact test to compare proportions. Results Thirty-six anti-TNF, 12 abatacept, and 16 patients on conventional synthetic DMARDs (csDMARDs) only were recruited. A higher proportion of CD4 and CD8 Temra (age-adjusted p = 0.004 and p = 0.0007 respectively) was observed in RA patients on anti-TNF with persistent disease compared to those in remission. This difference in Temra frequency was not observed in patients treated with csDMARDs only or abatacept. CD4 and CD8 Temra frequency correlated positively with CMV IgG levels (Spearman r = 0.8987, p Conclusion The increased CMV seropositivity and Temra frequency in the context of persistent disease only in anti-TNF treated patients may provide a causal link between Temra and RA pathogenesis refractory to anti-TNF treatment. Disclosure S. Yeoh: Grants/research support; S.A.Y. has received funding for research from Versus Arthritis, Royal College of Physicians, Rosetrees Trust, University College London Hospitals NIHR BRC and UCLH charities. J. Kimpton: None. M. Shipa: Grants/research support; M.S. has received funding for research from Versus Arthritis and GSK. E. Hawkins: None. A. Akbar: Grants/research support; A.A. has received funding for research from the Medical Research Council and the Leo Skin Foundation (Denmark). M. Ehrenstein: None.

Background/Aims Previous research into B cell biomarkers of poor response to the anti-CD20 drug rituximab in autoimmune disease relates to insufficient B cell depletion. Expansion of memory B cell (MBC) subsets were also associated with poorer response. We investigated whether the relative expression of the target antigen CD20 on B cell subpopulations could also contribute to drug resistance. Methods Peripheral blood samples from 6 rituximab naïve (RTX-N) patients with autoimmune rheumatic diseases (active systemic lupus erythematosus and rheumatoid arthritis), 6 patients previously treated with rituximab (RTX-T), and 6 healthy controls (HC) were obtained. B cell subpopulations were defined using the relative expression of IgD and CD27 using flow cytometry. Results Patients in the RTX-N group had significantly higher frequency of CD19+CD20- B cells (median=25.9% of total B cells, compared to 1.26% in HC), p = 0.0022. CD19+CD20-B cells were predominantly switched MBC (IgD-CD27+) and double negative (IgDCD27-) MBC cells. All patients in the RTX-T group (median 22 months post-rituximab) had detectable CD19+CD20- B cells (median=52.25% of total B cells), of which the majority were switched MBC (median=4.54%, range 0.23-74%) and DN B cells (median=53.5%, range 11.6-98.1%). Collectively, we noted that the frequency of CD19+CD20- B cells in peripheral circulation was higher in RTX-T>RTX-N>HC. Conclusion Our preliminary results have identified greater frequency of CD19+CD20- population of B cells in peripheral blood of patients with autoimmune disease, particularly after treatment with rituximab, suggesting that they evade rituximab. These are predominantly of the switched MBC and DN B cell subpopulations. Given the potential of these cells to contribute to disease activity in autoimmune disease, alternative strategies targeting CD19 may help overcome rituximab resistance. Disclosure K. Shah: Grants/research support; Roche Glycart. C. Klein: Corporate appointments; Roche Glycart. Shareholder/stock ownership; Roche. G. Cambridge: None. D. Sen: None. M. Castelino: None. A. Akbar: None. D.A. Isenberg: None. M. Leandro: None. V.R. Reddy: Grants/research support; Roche Glycart, BRC UCLH.

Resolving inflammation is thought to return the affected tissue back to homeostasis. However, we show that within days following resolution of Streptococcus pneumonia-triggered lung inflammation there is an influx of antigen specific lymphocytes with a memory and tissue-resident phenotype as well as macrophages bearing an alveolar or interstitial phenotype. Transcriptomic analysis revealed that macrophages are enriched with genes that drive T cell chemotaxis and differentiation as well as prostaglandin biosynthesis. Therapeutic depletion of post-resolution macrophages or inhibition of PGE2/EP4 signalling reduced numbers of lung CD4+/CD44+/CD62L+ and CD4+/CD44+/CD62L-/CD27+ T cells as well as their expression of the alpha-integrin, CD103. This intervention resulted in a failure of these cells to reappear and reactivate upon secondary challenge up to six weeks following primary infection. Concomitantly, EP4 inhibition caused accumulation of lung macrophages and marked tissue fibrosis. Hence, resolving inflammation triggers a second wave of immune activity controlled, in part, by PGE2, which through EP4, drives local tissue-resident T cell development on the one hand, whilst limiting tissue injury on the other.