IgM, IgA and IgG class serum antibodies against Klebsiella pneumoniae and Escherichia coli lipopolysaccharides in patients with ankylosing spondylitis. 
Igm, IgA and IgG class serum antibodies against Klebsiella pneumoniae and Escherichia coli lipopolysaccharides (LPS) were studied by ELISA in two separate AS patient populations of 99 and 81 subjects and in 102 healthy blood donors.  In the first patient population increased levels of IgM and IgG class antibodies against K. pneumoniae LPS were observed in patients with active AS.  In the population with active AS, increased levels of IgM, IgA and IgG class antibodies against K. pneumoniae LPS and IgA class antibodies against E. coli LPS were observed.  Sulphasalazine treatment decreased IgM and IgA class antibody levels significantly against K. pneumoniae LPS and IgM class antibodies against E. coli LPS.  These findings suggest that a significant part of the anti-Klebsiella antibodies found in AS patients is directed against the LPS component of Klebsiella.