Gel filtration: a new method to analyze and separate red blood cells with different deformabilities

Filtration of red blood cells through agarose gels (Sephadex, Sepharose, and Superose) was used to assess red cell deformability and simultaneously obtain fractions of red cells with different properties. The hemoglobin concentration in each fraction was used to define a filtration profile of red cells. It was found that gel filtration was a reproducible process. A gel filtration index (GFI) was derived from the height and the width of the filtration curve at half the maximum height. Osmotically treated red cells, red cells partially hardened with increasing glutaraldehyde concentrations, and mixtures of normal and hardened red cells were used to test the method. Changes in red cell deformability were sensitively detected by the GFI. The first fractions eluted from the column contained red cells with normal deformability, whereas the later fractions contained primarily less deformable cells with an increased membrane elastic modulus. By repeated filtration of late fractions it was possible to enrich the suspensions with less deformable cells. Patients with chronic renal failure had a decreased filterability; their GFI was 1.04 +/- 0.27 (n = 15) compared with 1.18 +/- 0.17 in controls (n = 20, p less than 0.05). We conclude that gel filtration is useful to detect and isolate abnormal red cell subpopulations. It could be a valuable tool for the investigation of disorders such as sickle cell anemia.