Antiglobulin factors in sera from patients with rheumatoid arthritis and normal subjects. Quantitative estimation in different immunoglobulin classes.

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Abstract
Antiglobulin factors in different immunoglobulin classes in human sera can be identified and measured by a technique involving absorption to and elution from insoluble preparations of rabbit IgG. The eluted anti-globulins are assayed by radial immunodiffusion in agar containing the specific anti-immunoglobulin. IgM antiglobulins were present in all and IgA antiglobulins in 14 out of 27 sera from rheumatoid patients with positive SCAT [serum complement agglutination test], neither were detectable in 25 normal sera tested. All sera contained IgG antiglobulins, the level in the patients'' sera being significantly higher than that in the normal subjects. The distribution of anti-globulins among the different immunoglobulins supports the view that rheumatoid factors arise as an antibody response, presumably to modified host IgG. The method employed can be applied generally to the quantitative estimation of antibodies in different immunoglobulin classes (and even in subclasses), provided the antigen can be prepared in an insoluble form.