Sheep red cells coated with rabbit IgG antibody may be used to detect IgM rheumatoid factors either by agglutination or microscopically by the fluorescence of antihuman IgM antibody conjugate bound to rheumatoid factors on the cell surface. By substituting for red cells the plastic surface of a filter disc coated with rabbit IgG it was possible to elute the bound conjugate and measure the fluor...
