Centrifugation of normal and rheumatoid arthritis blood on Ficoll-Hypaque and Ficoll-Nycodenz solutions.

Attempts to use the rapid single-step Ficoll-Hypaque centrifugation procedure for the purification of mononuclear and polymorphonuclear leucocytes from the blood of normal individuals and rheumatoid arthritis patients have sometimes been unsuccessful, largely because the erythrocytes would not sediment through the centrifugation medium. Re-evaluation of the factors (e.g. Ficoll concentration, temperature, and ratio of the diatrizoate salts) which affect these separations showed that under our conditions it was advantageous to use a medium with a lower viscosity (Ficoll concentration) and/or a higher osmotic strength (increased sodium diatrizoate: meglumine diatrizoate) than had been recommended previously (Ferrante and Thong, 1978; 1980; Ferrante et al., 1982). Higher osmotic strength media must be used for separating the components of blood from rheumatoid arthritis patients than from normal individuals because rheumatoid arthritis erythrocytes have a lower buoyant density than normal erythrocytes.