LOW-MOLECULAR-WEIGHT RHEUMATOID FACTOR*

Abstract

Rheumatoid sera with and without acid dissociable intermediate complexes were studied by means of ultracentrifugation, chromatography and sulfhydryl reagents. In sera containing intermediate complexes, rheumatoid factor activity was found in the 7S regions of density gradients and in pre-albumin chromatographic fractions as well as in 19S regions. Control rheumatoid and non-rheumatoid hypergamma-globulinemic sera contained rheumatoid factor in the 19S regions only. Activity was completely abolished in control sera made 1 [image] with 2-mercaptoethanol while considerable reactivity remained in similarly treated sera with intermediate complexes. These studies indicate the existence, in rheumatoid sera with intermediate complexes, of a low molecular weight rheumatoid factor which may be analogous to the 7S counterparts of normal macroglobulin antibodies.