Surface differences between erythrocytes from arbitrarily chosen (presumably hematologically normal) individuals detected by cell partitioning.

Differences in membrane surface properties (both charge-associated and lipid-related) of erythrocytes from any two arbitrarily selected individuals can be detected by use of a purely physical method: cell partitioning in dextran-poly(ethylene glycol) aqueous phase systems. The procedure consists of isotopically labeling (with [51Cr]-chromate) aliquots of red blood cell populations to be compared. Such labeled cells are mixed with an excess of unlabeled erythrocytes from the other individual and the mixtures subjected to countercurrent distribution in either a charge-sensitive or a non charge-sensitive aqueous phase system. As control we also prepare mixtures of labeled cells with unlabeled cells from the same individual to ascertain that the label per se has no influence on the cells' partitioning behavior. The distribution curves are analyzed for total cells (in terms of hemoglobin absorbance) and labeled cells (in terms of counts/min). Changes in the relative specific activities through the distribution curves are routinely obtained when cells from different individuals are used and are indicative of subtle differences in surface properties of such erythrocyte populations.