Autoinhibition of Rheumatoid Factor Reactivity Demonstrated by a Block Hemagglutination Procedure

摘要

Various rheumatoid factor (RF) sera were titrated with human γ-globulin (HGG) coated tanned sheep cells at six cell concentrations ranging from 0.125% to 2.0%. It was found that in 36 of 63 sera tested there was an abnormally large decrease in titer with increasing cell concentration. Double logarithmic plots of titers vs . cell concentrations were linear. While linearity with a slope of -1.0 was to be expected, it was found that these 36 sera tested yielded slopes greater than -1.0.Addition of aggregated HGG to a -1.0 slope serum caused a rise in slope. Removal of autologous 7 S HGG, by diethylaminoethyl (DEAE) column chromatography, from a high slope serum lowered the slope. Addition of 7 S HGG, prepared either from a high slope serum or from certain normal sera, to a -1.0 slope serum served to raise the slope. Partial removal of RF by adsorption of a low slope serum also caused an increased slope. Heating at 56°C for 30 min did not affect slope values.These results suggest that the high slope effect is primarily due to autoinhibitory heat stable components present in the 7 S HGG fraction of most rheumatoid factor sera.