title: ELISA estimations of rheumatoid factor IgM, IgA, and IgG in sera from RA patients with high disease activity. DTT treatment studies.
abstract: Although Elisa assays detecting rheumatoid factor's (RF) show high sensitivity and specificity, difficulties with IgA- and especially IgG-RF testing in ELISA systems, due to interaction from 'contaminating' IgM-RF is still thought to be a problem. Sera from 15 Rheumatoid Arthritis patients with high disease activity and high IgM-RF values were Dithiothreitol (DTT) treated. IgM-RF values were reduced to approximately zero in all tested sera. IgA-RF activity declined as expected, but also showed a statistically significant correlation between % reduction after DTT treatment and the IgM-RF value from the same serum sample. IgG-RF also decreased after DTT treatment, most pronounced for high IgG-RF values. A correlation (not statistically significant) between the % reduction in IgG-RF after DTT treatment and the IgM-RF value from the same serum sample was observed. Pepsin and Diethylammonium ethyl (DEAE) reduced the IgG-RF activity even more than after DTT treatment of the sera. Fractionation by Gel filtration of 8 serum samples showed that all the RF activity were found according to the 'first top' of the gel filtration curve.
authors.affiliation: Department of Clinical Immunology, Aalborg Hospital, Denmark.
authors.forename: G T
authors.initials: GT
authors.lastname: Espersen
authors.forename: E
authors.initials: E
authors.lastname: Ernst
authors.forename: M
authors.initials: M
authors.lastname: Vestergaard
authors.forename: N
authors.initials: N
authors.lastname: Grunnet
mesh_terms: D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology; D002850:Chromatography, Gel; D004229:Dithiothreitol / Q000627:therapeutic use*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D012217:Rheumatoid Factor / Q000032:analysis*
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012217:Rheumatoid Factor; D004229:Dithiothreitol