Quantitation of cells secreting rheumatoid factor of igg, iga, and igm class after elution from rheumatoid synovial tissue

In an indirect hemolytic plaque assay that used sheep erythrocytes coated with normal rabbit IgG or reduced/alkylated IgG anti–sheep erythrocytes, mononuclear cells eluted from rheumatoid synovial tissue of 7 of 11 patients with seropositive rheumatoid arthritis contained cells that secreted rheumatoid factor of IgG, IgA, and IgM classes. The number of rheumatoid factor–secreting cells varied from <1% to 53% of the total number of eluted immunoglobulin‐secreting cells. In contrast, immunoglobulin‐secreting cells and rheumatoid factor–secreting cells were scanty in blood compared with synovial tissue mononuclear cells.