Clonally restricted anti‐igg antibodies in rheumatoid arthritis

Abstract

Clonally restricted anti‐IgG antibodies were detected, by isoelectric focusing (IEF) and chromatofocusing techniques, in the sera of patients with rheumatoid arthritis (RA). Anti‐Fab antibodies were predominantly acidic proteins with isoelectric points of 4.5–6.5 and displayed restricted spectrotype patterns. Proteins reactive with the Fc portion of IgG showed polyclonal spectrotype patterns with alkaline pI of 7.5–9.0. A limited array of anti‐Fab spectrotypes was consistently detected in RA sera when analyzed by IEF on 6M urea gels. Additional anti‐Fab antibody bands were detected when the RA sera were dialyzed against 4–6M urea prior to IEF analysis, indicating that some anti‐Fab antibodies exist in a complexed form in serum. Under these dissociating conditions, anti‐Fab antibodies could also be detected in normal subjects, but the spectrotype patterns were more restricted than those in RA sera. Because anti‐Fab antibodies may regulate normal immune responses, the increased quantity of clonally restricted anti‐Fab antibodies in RA may indicate an abnormality of this immunoregulation.