Nuclear BCL10 in primary Sjögren's syndrome

Background: The events following triggering of antigen receptors and subsequent activation of the transcription factor nuclear factor kappa B (NFκB) need to be carefully controlled to prevent abnormal immune responses. BCL10 links the antigen receptor to NFκB. The aim of this study was to determine the expression pattern of BCL10 and NFκB in minor salivary gland infiltrates of patients with primary Sjögren’s syndrome (pSS). Methods: Minor salivary glands from patients with primary SS (n = 17) and sicca controls (n = 4) were evaluated by single and double immunohistochemistry and immunofluorescence for confocal microscopy. BCL10 and NFκB‐p65 expression were evaluated in the infiltrating lymphocytes. Ectopic germinal centers (GCs) were investigated by CD21. Tonsil, lymph node and lymphoma tissue were used as positive controls. Results: BCL10 nuclear positive cells were observed in focal lymphocytic infiltrates in the investigated minor salivary glands and were not restricted to patients with ectopic GCs. By double‐staining, some of the BCL10 nuclear positive cells were identified as B cells. There was, however, no constitutive activation of NFκB as depicted by the exclusive cytoplasmic expression of p65 in the infiltrating lymphocytes in the pSS. Conclusion: Nuclear expression of BCL10 in infiltrating lymphocytes was a common occurrence in pSS minor salivary glands indicating it as a possible marker of autoimmune induced chronic inflammation. There was, however, no constitutive activation of NFκB.