Background/Purpose: Spondylarthropathies (SpA) comprise a group of rheumatic diseases such as ankylosing spondylitis (AS), arthritis/spondylitis with inflammatory bowel disease, arthritis/spondylitis with psoriasis (PsA), reactive arthritis (ReA) and undifferentiated spondyloarthritis (uSpA). Their genetic background, familial aggregation, pathophysiology and overlapping clinical manifestations suggest a common origin between them. Previous trials have suggested the role of the intestinal mucosa in the etiopathogenesis of SpA. Increased serum levels of IgA and secretory IgA (SIgA) in AS patients have also been reported, but whether SIgA has a role in the pathogenesis of ReA and uSpA remains unknown.

Methods:  Cross sectional study. Serum concentrations of SIgA and total IgA were measured using ELISA and nephelometry in patients and healthy subjects. Activity indices (BASDI, Ankylosing Spondylitis Disease Activity Score (ASDAS)) were applied in each patient. Statistical analysis was performed using Stata 11.2® software for Windows. t Student test was used to compare different groups or subgroups. Pearson correlation was used to measure the correlation degree between SIgA, IgA and disease activity. Multiple linear regression models were used to evaluate the strength of the association. The study was approved by the hospital’s ethics committee.

Results:  46 patients (78,2% men, mean age 34,8±12,3y) and 53 controls (41% men, mean age 32y) were included. The mean serum levels of SIgA were higher in patients (19,85±9,97 µg/ml) than in healthy subjects (10,82 ±6,5 µg/ml p <0.000). Mean total IgA levels did not show statistical differences between patients and healthy subjects (275±123 mg/dl vs 284,33±107 p=0,72). SIgA levels correlated with disease activity in patients using the following activity index: BASDI (r= -0.42, p=0.0046), ASDAS-CRP (r= -0.37, p=0.014) and ASDAS-ESR (r= -0.45, p=0.0021). Negative correlation between SIgA and all activity index was higher in HLA-B27⁺ patients (BASDI r= -0.70, p=0.0009, ASDAS-CRP r= -0.58, p=0.0093 and ASDAS-ESR r= -0.57, p=0.0083) than in HLA-B27^– patients. Multivariate regression models showed linear association between SIgA and BASDI (-0,12 p=0,005), ASDAS-CRP (-0,04 p=0,014) and ASDAS-ESR (-0,048 p=0,002). Table 1.

Conclusion:  High serum levels of SIgA were associated with decreased activity in patients with ReA and uSpA. SigA is a very important molecule participating in host defense of intestinal mucosa, playing an important role in homeostasis. These findings highlight the importance of the development of new studies to reach a better understanding of the role of the intestinal mucosa in the different SpA phenotypes.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/does-secretory-immunoglobulin-a-influence-disease-activity-in-patients-with-reactive-arthritis-and-undifferentiated-spondylarthritis/