RT Journal Article SR Electronic(1) A1 Senior, B. W. A1 Mcbride, P. D. P. A1 Morley, K. D. A1 Kerr, M. A.YR 1995 T1 The detection of raised levels of IgM to Proteus mirabilis in sera from patients with rheumatoid arthritis JF Journal of Medical Microbiology, VO 43 IS 3 SP 176 OP 184 DO https://doi.org/10.1099/00222615-43-3-176 PB Microbiology Society, SN 1473-5644, AB Summary An analysis by ELISA of 100 rheumatoid factor (RF)-positive sera selected at random from a collection of sera from patients with various auto-immune diseases and joint pains, and 100 RF-negative sera from the same collection matched by patient age and gender, showed that the RF-positive sera had highly significantly (p ≪ 0.0001) raised levels of IgM antibody, but not IgG antibody, to Proteus mirabilis over those of the RF-negative sera. This response was subsequently found to be associated with sera from patients who clinically had rheumatoid arthritis (RA). Sera from the RA patients had significantly greater amounts (p = 0.026) of IgM antibody to P. mirabilis than to the other organisms tested and these values were also highly significantly different (p ≪ 0.0001) from P. mirabilis IgM antibody levels in matched RF-negative sera. Sera from RA patients also had significantly greater amounts of IgA to P. mirabilis (p ≪ 0.0001) and greater amounts of IgM to Escherichia coli (p ≪ 0.0001) and Klebsiella pneumoniae (p ≪ 0.0001) than those in matched RF-negative sera. Other classes of antibody to these organisms and all classes of antibody to Pseudomonas aeruginosa were not raised in the sera of RA patients over those of RF-negative controls. The IgM response in RA patients was not specific for only one O serotype of P. mirabilis but was associated with all 11 different O serotypes of P. mirabilis tested and those of other Proteus spp. Moreover, the IgM antibodies to Proteus spp. appeared to be independent from C-reactive protein and RF. Fourteen of 27 sera from RA patients had an IgM antibody that reacted with an internal 90-kDa protein of P. mirabilis. This antibody was not found in RF-positive sera of patients with Sjogren’s disease or systemic lupus erythematosus, nor in other RF-negative sera, nor in those of healthy people, nor in those with osteoarthritis or ankylosing spondylitis. IgM antibodies capable of reacting with the haemolysin protein Hpm B of P. mirabilis were not found in sera of RA patients of unknown HLA status., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-43-3-176