POS0177 POTENTIAL INVOLVEMENT OF IL-40 AND IL-40-PRODUCING CELLS IN PRIMARY SJOGREN’S SYNDROME (pSS) AND pSS-ASSOCIATED LYMPHOMA

Abstract

Background:The pathogenesis of pSS relies on a complex interplay between both innate and adaptive immune responses in which B cells play a pivotal role. Their chronic aberrant hyperactivation may drive clonal escape and consequent lymphomagenesis [1]. In the last few years, B cells have emerged as potential effector cells, able to release a wide range of cytokines that actively contribute to shape the microenvironment they act in. Recently, IL-40, a novel B cell associated cytokine encoded by an uncharacterized gene (C17orf99; chromosome 17 open reading frame 99) was described. Naïve B cells can express IL-40 at both tissue and peripheral level and the stimulation of B cells with IL-4 and TGF-β significantly increases IL-40 release. In addition, human B cells lymphomas are able to constitutively produce IL-40 [2]. Taking into account this emerging evidence and considering the well-known role of IL-4 and TGF-β in pSS pathogenesis, as well as the association with lymphomas, we decided to focus our attention on IL-40 in pSS patients.Objectives:The aim of the present study was to investigate IL-40 expression in the salivary glands of patients affected by pSS and pSS-associated non-Hodgkin’s lymphoma (NHL).Methods:Minor salivary gland biopsies were obtained from 22 patients with pSS and 12 patients with non-specific chronic sialoadenitis (nSCS), included as controls. Paraffine-embedded samples of parotid glands from patients with a previous diagnosis of pSS-associated NHL (n=10) were selected from the biopsy bank of the Pathology Unit of the Ospedale Cervello (Palermo, Italy). Quantitative gene expression analysis by TaqMan real-time PCR and immunohistochemistry (IHC) for IL-40, IL-4, TGF-β1 was performed on salivary glands from patients and controls. The cellular sources of IL-40 among infiltrating inflammatory cells were determined by fluorescence-activated cell sorting (FACS) analysis and immunofluorescence (IF). Serum IL-40 levels were measured by ELISA in both patients (n=10) and controls (n=9).Results:IL-40 was significantly increased at both protein and mRNA level in the inflamed salivary glands of patients with pSS where a positive strong correlation between the IL-40 mRNA levels and the focus score (FS) was evidenced. The expression of IL-40 in parotid glands of pSS-associated NHL was also markedly increased (Figure 1). IL-40 expression correlated with the presence of IL-4 and TGF-β; both cytokines were significantly increased in pSS at mRNA and protein level. Among infiltrating immune cells, CD19+ B cells resulted the major source of IL-40. However, we identified CD4+, CD8+ T cells and CD68+ macrophages as additional producers of IL-40 in both FACS and IF analysis. The ELISA test also showed a significant increase of serum IL-40 concentration in pSS patients (p value = 0.0190), compared to controls.Conclusion:Our preliminary results suggest that IL-40 may play a role in the pathogenesis of pSS and pSS-associated NHL. To the best of our knowledge, this is the first demonstration of the overexpression of this cytokine in salivary gland tissue and sera in pSS. Moreover, we demonstrated that IL-40 is produced by several cellular types, such as T cells and macrophages, and is not exclusively released by B cells. Further studies are necessary to clarify IL-40 pathways and functions in order to unravel IL-40 possible role in pSS development.