Serum levels of IgG, IgM, and IgA in rheumatoid arthritis.

The role of immunoglobulins in the pathogenesis of rheumatoid arthritis (RA) has been studied by Franklin and Kunkel (1957), Hamerman (1966), and Hollander, McCarty, Astorga, and CastroMurillo (1965). The inconstancy of the reported presence of the rheumatoid factor (RF), which is considered by Franklin and Kunkel to be a complex composed of altered IgG bound to a molecule of IgM, and also the variability of serum levels of gamma globulins as determined by simple or immuno-electrophoresis has led us to study these levels by more specific analytical procedures. We have compared the levels of IgG, IgM, and IgA by quantitative immunoprecipitation according to the method of Mancini, Vaerman, Carbonara, and Heremans (1964), modified by Fahey and McKelvey (1965), and have related the results to the clinical stage, the duration of disease, the rheumatoid factor titre, and the patient's age.