Patients with rheumatoid arthritis (RA) are at increased risk of diffuse large B cell lymphoma (DLBCL) compared to the general population. Here, we explored the inflammatory profiles in the blood of RA patients who had developed DLBCL. RA-DLBCL patients had significantly higher levels of the pro-inflammatory markers TNF, IL-8, CXCL9, APRIL, and particularly CXCL13 (median 796 vs. 206 pg/mL, p = 0.001), compared to RA controls. By including an extensive autoantibody panel of rheumatoid factor, IgG anti-CCP2, anti-citrullinated protein antibodies (ACPA) fine-specificities, and other anti-modified protein antibodies, all RA-DLBCL patients were autoantibody seropositive. Yet, RA-DLBCL patients did not display significantly different autoantibody signatures compared to RA controls. The levels of immunoglobulin free light chains and C-reactive protein were similar in RA-DLBCL patients and RA controls. In conclusion, RA-DLBCL patients exhibit pro-inflammatory signatures with elevated markers that are important for B cells and may contribute to enhanced B-cell activation and promote lymphoma development.

Simple Summary Immunotherapy blocking programmed cell death protein 1 (PD-1) and its ligands (PD-L1, PD-L2) is less effective in non-Hodgkin lymphoma (NHL) than classical Hodgkin lymphoma. However, NHL is a heterogeneous group and current research seeks to identify subgroups of NHL patients responsive to PD-1 blocking agents. Whether patients with pre-existing rheumatic diseases might constitute such a subgroup is unknown. We investigated the expression of PD-1 and its ligands in lymphoma patients with pre-existing rheumatic diseases. Our key findings include that in patients with pre-existing rheumatoid arthritis (RA) and subsequent diffuse large B-cell lymphoma, an association between RA disease severity and increased expression of PD-L1 in tumor cells was seen. This warrants further studies of the PD-1 pathway in lymphoma in other chronic inflammatory conditions. Current research seeks to identify subgroups of non-Hodgkin lymphoma (NHL) patients responsive to PD-1 blocking agents. Whether patients with pre-existing rheumatic diseases might constitute such a subgroup is unknown. We determined intratumoral expression of PD-1 and its ligands in lymphoma patients with pre-existing rheumatic diseases. We included 215 patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) or Sjogren's syndrome with subsequent lymphoma and 74 diffuse large B-cell lymphoma (DLBCL) controls without rheumatic disease. PD-1 and PD-ligand immunohistochemical markers were applied on tumor tissue microarrays. The number of PD-1+ tumor infiltrating leukocytes (TILs) and proportions of PD-L1+ and PD-L2+ tumor cells and TILs were calculated and correlated with clinical data. Expression of PD-L1 in tumor cells and TILs was highest in classical Hodgkin lymphoma and DLBCL. In DLBCLs, expression of PD-1 in TILs and PD-L1 in tumor cells was similar in RA, SLE and controls. In RA-DLBCL, high expression of PD-L1 in tumor cells was significantly more common in patients with the most severe RA disease and was associated with inferior overall survival in multivariable analysis.

Several autoimmune and inflammatory conditions, such as rheumatoid arthritis (RA) and primary Sjögrens’s syndrome (pSS), have repeatedly been linked to an increased risk of malignant lymphoma [1,2]. Certain inflammatory conditions are also associated with the development of specific lymphoma subtypes such as mucosa-associated lymphoid tissue (MALT) lymphoma in pSS and diffuse large B-cell lymphoma (DLBCL) in RA. The underlying mechanisms behind this association remain unclear. The highly increased risk of developing MALT lymphoma of the parotid gland in pSS indicates that local inflammatory processes can promote lymphoma development at the site of chronic inflammation [3]. In RA, an association between disease severity and risk of lymphoma has been shown.

Granulomatosis with polyangiitis (GPA), formerly Wegener’s granulomatosis, is a systemic small vessel vasculitis associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA) and characterized by granulomatous inflammation and necrotizing vasculitis of the airways and kidneys but possibly affecting any organ system. An increased risk of lymphoma in patients with GPA has been reported in several epidemiological studies [4,5]. However, very little is known about risk factors for lymphoma development in this group, possible relation to disease severity, treatment and lymphoma subtypes or the prognosis for the lymphomas. This is the first published study on GPA and lymphoma, giving detailed information on the GPA characteristics and possible risk factors for lymphoma and also lymphoma subtypes treatment and survival.