<h3>Background</h3> The human Major Histocompatibility Complex (<i>MHC</i>) 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. <h3>Objectives</h3> The 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. <h3>Methods</h3> The 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 hospital9s ethics committee. <h3>Results</h3> 46 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. <h3>Conclusions</h3> These results suggest that SIgA levels in patients with ReA and USpA might be a correlate of disease activity measures based upon HLA-B27 status and might reflect an immunomodulatory role in these pathologies. <h3>References</h3> Bowness P. HLA-B27. Annu Rev Immunol. 2015; 33:29–48. Chatzikyriakidou A, Voulgari PV, Drosos AA. What is the role of HLA-B27 in spondyloarthropathies? Autoimmun Rev. 2011 Jun; 10(8):464–8. <h3>Disclosure of Interest</h3> None declared