AB0674 Secretory IGA: Negative Correlation with Disease Activity Measures in HLA B27 Positive Spondyloarthritis Patients

BackgroundThe human Major Histocompatibility Complex (MHC) encompasses a group of genes located in chromosome 6 (6p21.3); it encodes proteins expressed on the cell surface. The HLA-B27 is a MHC class I molecule associated with spondyloarthritis (SpA); many theories related to its natural function have been postulated to explain its pathogenic role.(1–2) Relevance of HLA-B27 molecule in the mucosal immune system, the gut mucosa inflammation, and secretory IgA (SIgA) production remains unresolved.ObjectivesThe purpose of this study was to evaluate the correlation between serum SIgA levels and disease clinical activity in a cohort of HLA B27 positive and negative SpA patients with ReA and USpA, in a clinical center in Bogota Colombia.MethodsThe concentration of SIgA in serum was measured by an enzyme linked immunosorbent assay and the HLA-B27 was assessed by flow cytometry, followed by Polymerase Chain Reaction with sequence specific primers, in 46 patients with USpA and ReA. Clinical gastrointestinal manifestations and activity indices (BASDAI, ASDAS x CRP and ASDAS x ESR) were collected from each patient. Statistical analysis was performed using Stata 11.2 ® software for Windows; Pearson correlation was used to measure the degree of relationship between SIgA and clinical activity depending on the HLA B27 status. The study was approved by local hospital's ethics committee.Results46 SpA patients completed the study with mean age of 34,8 ±12,3 years; 78,2% were men, 52,17% were HLA B27 positive, 60.9% of patients reported gastrointestinal symptoms such as diarrhea, abdominal pain, abdominal swelling and hematochezia. 63,6%, 88,6% and 100% of patients had disease activity evaluated by BASDAI, ASDAS-CRP and ASDAS-ESR scores, respectively, and 71,7% of patients had SIgA concentration above the upper normal range. The SIgA concentration was correlated with disease activity measures: BASDAI, ASDAS-CRP and ASDAS-ESR (-42% (0.0046), -37% (0.014) and -45% (0.0021) respectively); the negative coefficient correlation between SIgA and BASDAI, ASDAS-CRP and ASDAS-ESR was higher in HLA-B27 + patients -70% (0.0009), -58% (0.0093) and -57% (0.0083) than in HLA-B27 – patients.CorrelationHLA-B27 positiveHLA-B27 negativePearson CoefficientP valuePearson CoefficientP valueSIgA vs BASDAI−70%0.0009−21%0.3397SIgA vs ASDAS-CRP−58%0.0093−20%0.3579SIgA vs ASDAS-ERS−57%0.0083−35%0.0992ConclusionsThese results suggest that SIgA levels in patients with ReA and USpA might be a correlate o