POS0782 FOLLICULAR DENDRITIC CELL NETWORKS IN MINOR SALIVARY GLAND BIOPSIES: A MARKER OF DISEASE ACTIVITY AT BASELINE AND DURING THE FOLLOW-UP IN SJÖGREN’S SYNDROME

Background:Minor salivary gland biopsy (MSGB) has been increasingly recognized as an important tool for the stratification of patients with primary Sjögren’s syndrome (pSS). Recently, the presence of follicular dendritic cell (FDC) networks in the inflammatory infiltrate has been associated with more severe biological and serological abnormalities compared with less organized infiltrates.Objectives:To investigate the associations between the presence and number of FDC networks in foci and pSS glandular and extra-glandular disease activity at baseline and during the follow-up.Methods:Consecutive MSGBs performed in daily practice for clinically suspected pSS from January 2017 to October 2020 were reviewed. Patients’ demographic, clinical, biological and serological data were obtained from medical records. The ESSDAI was used to measure disease activity at baseline and at the end of the follow-up in pSS patients. For histopathology, 3 µm sections were cut from each formalin-fixed paraffin-embedded block of MSGBs and stained with haematoxylin and eosin (H&E). Immunohistochemical stainings were performed on additional 3 μm sections in order to detect T lymphocytes (CD3), B lymphocytes (CD20) and follicular dendritic cells (CD21). Glandular tissue areas, number of foci, focus score (FS) and the presence and number of FDC networks were assessed.Results:We reviewed 330 consecutive MSGBs from patients with suspected pSS: out of them 146/330 (44%) were classified as nonspecific chronic sialadenitis (NSCS) whereas 184/330 (56%) as focal lymphocytic sialadenitis (FLS). According to the ACR/EULAR criteria the diagnosis of pSS was confirmed in 130 patients (117 F:13 M, age 56±13 yrs). The mean (S.D) surface area of the MSGBs was 7.8 (3.9) mm2. The number of foci in the FLS samples ranged from 1 to 12 (mean (S.D)=3.1 (2.6)), whereas the FS ranged from 0.3 to 9.0 (mean (S.D) = 1.4 (1.2)).The presence of FDC networks was documented in 106/330 (32%) of the samples; in 54/106 (51%) of these MSGBs the number of FDC networks ranged from 2 to 8 (mean (S.D)=3.1 (1.4)). The number of FDC networks significantly correlated with the number of foci (r=0.721**) and FS (r=0.707**). Patients with FDC networks in the inflammatory infiltrate presented more serological abnormalities (i.e anti-Ro/SSA, anti-LA/SSB, Rheumatoid factor) and elevated IgG levels (p<0.001). In pSS patients, the number of FDC networks slightly correlated also with C4 levels (r=-0.216*), peripheral lymphocyte count (r=-0.274**) and with glandular (r=0.213*), and biological (r=0.230**) domains of the ESSDAI at baseline. After a mean (S.D) follow-up of 21(13) months, the number of FDC networks still correlated with the final total ESSDAI (r=0.312**).Conclusion:The presence and number of FDC networks in foci represent a useful histopathological parameter able to reflect disease activity at baseline and during the follow-up, thus allowing more personalized interventions.Disclosure of Interests:None declared