1.Introduction
Primary Sjogren’s syndrome(pSS) is a complex autoimmune disease, which is characterized by the infiltration of lymphocytes from exocrine glands, leading to the dysfunction of gland secretion, and then a series of symptoms of gland injuries, such as dry mouth, dry eye and swelling of parotid gland, as well as extraglandular manifestations such as arthralgia, interstitial lung disease(ILD), renal tubular acidosis and primary biliary cholangitis(PBC),and part of patients have systemic manifestations, such as fatigue, fever and weight loss[1, 2]. Until now, the pathogenesis of pSS has not been clarified.Generally speaking, the pathogenesis of pSS is related to environmental factors,genetic susceptibility and immune disorder.It is well known that pSS is mainly mediated by T cells and B cells, but innate immune cells such as NK cells also play an important role in the pathogenesis of pSS[3].Recent studies have found that the expression of NK cells in peripheral blood or salivary glands of pSS patients or model mice was abnormal, which was related to the activity and severity of the disease[4-6].
CD161 is one of a member of human NKRP1 subfamily which is called NK cell receptor protein 1A (NKR-P1A) or killer cell lectin-like receptor subfamily B member 1 (KLRB1),and it’s also a type II transmembrane C-type lectin glycoprotein receptor, which is called C-type lectin domain family 5 member B (CLEC5B)[7]. CD161 is mostly expressed on NK cells and T cell subsets such as CD4+T cells,CD8 αβT cells, γδT cells and NKT cells[8].In humans, the ligand of CD161 is called lectin-like transcript 1(LLT1),which is mainly expressed on activated monocytes and B cells, and interacts with CD161 to inhibit the activation of NK cells, and inhibit cytotoxic function and cytokine secretion mediated by NK cells[9, 10].
At present, the few research of CD161 in pSS patients is limited to T cells and the subsets of T cells[11, 12], and there is no relevant study on the clinical relevance of CD161 expression on NK cells in pSS patients.In this study,we detected the proportion of CD161 in peripheral blood on CD56+NK cells of pSS patients by flow cytometry, and analyzed the clinical correlation between the proportion of CD161+CD56+NK cells and disease activity in pSS. This research aims to provide new ideas and therapeutic targets for the diagnosis and treatment of pSS.