RHEUMATOID-FACTOR AS A CAUSE OF POSITIVE REACTIONS IN TESTS FOR EPSTEIN-BARR VIRUS-SPECIFIC IGM ANTIBODIES

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 36  (3) , 415-422
Abstract
Sera from 28 patients with rheumatoid arthritis (RA) were titrated in indirect immunofluorescence tests for Epstein-Barr virus (EBV) specific antibodies [Ab]. All had Ig[immunoglobulin]G Ab to viral capsid antigen (VCA), 64% at titers .gtoreq. 320, and 71% reached in tests for VCA-specific IgM Ab at titers ranging from 20-640. The reactions observed in the IgM test were not due to VCA-specific IgM Ab but rather to rheumatoid factor (RF), usually an IgM Ab to the Fc regions of IgG. The titers recorded in the anti-VCA IgM test correlated significantly with the RF titers and both reactivities were abolished by adsorption onto IgG-coated latex particles. They clearly depended upon the height of the IgG Ab titer to VCA, indicating that the more VCA-specific IgG molecules are present the more likely it is that RF will combine with them in sufficient quantity before or after their attachment to VCA-positive test cells so as to become detectable by the fluorescent Ab to human IgM. Results comparable in every aspect were obtained with those sera from patients with Hodgkin''s disease, nasopharyngeal or cervical carcinomas which reacted in the anti-VCA IgM test. Sera from patients with infectious mononucleosis may contain RF, but in such cases its removal by adsorption onto IgG-coated latex particles did not generally reduce the VCA-specific IgM Ab titer. Removal of RF from any of the sera studied did not affect the titers of VCA-specific IgG and, where applicable, IgA or heterophile Ab titers. The pitfall created by RF in tests for virus-specific IgM Ab is re-emphasized.