Investigations of Variables Affecting Rheumatoid Factor Reactivity and Tests: I. Influence of Amboceptor Concentration, Ratio of IgG to IgM, and Source, in the Sheep-cell Agglutination Test
Open Access
- 1 January 1974
- journal article
- research article
- Published by Oxford University Press (OUP) in American Journal of Clinical Pathology
- Vol. 61 (1) , 47-58
- https://doi.org/10.1093/ajcp/61.1.47
Abstract
Sucrose gradient purified IgG and IgM rabbit amboceptors were used in various concentrations and proportions to titrate rheumatoid factor (RF) by the sheep-cell agglutination test (SCAT) in rheumatoid arthritis (RA) and normal sera. By stepwise multiple-regression analysis, the patient serum variable, as expected, contributed most (43.2%) to variability. After eliminating the above variability, amboceptor concentration accounted for 81.4%, IgG:IgM ratio accounted for 14.2%, and amboceptor source accounted for 4.4%. The source of 20% of the total variability remained unknown. Individual high-titered RA sera when tested with various sensitizing dilutions of amboceptors showed a two-segment relationship: the first segment widi reactive titers, and the second consisting of an abrupt fall to nonreactive titers. Low-titered RA sera usually showed only the second segment. The presence of cell-absorbed IgM amboceptor did not interfere with the reaction between RF and cell-absorbed IgG amboceptor. The data indicate that the use of pure rabbit IgG amboceptor substantially reduces variation in the SCAT.Keywords
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