IgM, IgG, and IgA response to enterobacteria in patients with ankylosing spondylitis in southern India

IgM, IgA, and IgG response to three different antigenic preparations-lipopolysaccharide (LPS), culture supernatant proteins, and outer membrane protein (OMP) of Klebsiella pneumoniae, Escherichia coli and Salmonella typhi-were measured in the sera of 20 patients with primary ankylosing spondylitis (AS), 10 with enterogenic reactive arthritis (ReA) (disease controls), and 15 voluntary blood donors (healthy controls) by ELISA using biotinylated anti-human immunoglobulins M, G, and A. Serum immunoglobulin levels were measured by immunoturbidimetric assay in 20 AS patients, 20 patients with enterogenic reactive arthritis (ReA), 20 with ulcerative colitis (UC), and 20 voluntary blood donors. Student's t-test was applied for comparison. Compared to healthy controls, AS patients showed significantly elevated IgG response against culture supernatant proteins of all the three organisms (P <0.05), LPS of E. coli (P < 0.05) and Klebsiella (P < 0.005), as well as OMP only of Klebsiella pneumoniae. This was reflected as significantly elevated IgG level in AS compared to controls (P < 0.05 vs. ReA and 0.005 vs. UC and healthy controls). This suggests the involvement of outer membrane proteins of Klebsiella pneumoniae in the pathogenic mechanism of ankylosing spondylitis.