Background: Primary Sjogren's syndrome (SS) is an autoimmune disease with a strong predilection for lymphoma development, with earlier disease onset being postulated as an independent risk factor for this complication. Variations of the Leukocyte immunoglobulin-like receptor A3(LILRA3) gene have been previously shown to increase susceptibility for both SS and non-Hodgkin B-cell lymphoma (B-NHL) in the general population. We aimed to investigate whether variations of the LILRA3 gene could predispose for lymphoma development in the context of SS.
Methods: Study population, all of Greek origin, included 101 SS cases with a current or previous diagnosis of lymphoma (SS-lymphoma, SS-L) and 301 primary SS patients not complicated by lymphoma (SS-non-lymphoma, SS-nL). All SS patients fulfilled the 2016 SS American College of Rheumatology/European league against Rheumatism (ACR/EULAR) classification criteria. A total of 381 healthy controls (HC) of similar age/sex/race distribution were also included. On the basis of the age of SS onset and the presence or absence of adverse predictors for lymphoma development, SS patients were further stratified into younger (≤40 years) and older (>40 years) age of disease onset, as well as into high/medium and low risk groups. Polymerase chain reaction (PCR) was implemented for the detection of the following LILRA3 gene variants: homozygous non-deleted or functional wild type (+/+) heterozygous (+/-) and homozygous deleted (-/-). LILRA3 serum protein levels were quantitated by enzyme-linked immunosorbent assay (ELISA) in 85 individuals (29 SS-L, 35 SS-nL patients and 21 HC).
Results: While no statistically significant differences were detected in the overall frequency of LILRA3 gene variants between SS-L, SS-nL and HC groups, LILRA3 serum protein levels were increased in the SS-L group compared to HC (1.27 ± 1.34 vs. 0.38 ± 0.34 ng/mL, p-value: 0.004). After stratification according to the age of SS onset and history of lymphoma, as well as the presence or absence of adverse predictors for lymphoma development, the prevalence of the functional LILRA3 gene variant was found to be significantly increased in the young onset SS-L group compared to the HC of similar age and sex distribution (100% vs. 82.9%, p = 0.03), as well as in the high/medium risk SS compared to the low risk SS (91.3 vs. 78.3%, p = 0.0012). Of note, young onset SS-L and SS-nL groups displayed higher LILRA3 serum levels compared to their older counterparts (p-values: 0.007 and 0.0005, respectively).
Conclusion: The functional LILRA3 gene variant increases susceptibility to SS-related lymphoma development in patients with a disease onset of <40 years old, implying that genetically determined deranged immune responses in younger SS individuals could underly their pronounced risk for lymphoma development.
Keywords: LILRA3; Sjogren’s syndrome; chronic inflammation; genes; lymphoma.