A study on the erythrocyte aggregating properties of polybrene and protamine sulphate.

By observing the aggregation of erythrocytes in protamine sulphate or Polybrene it is possible to predict MN phenotypes with 97 per cent accuracy. It is probable that one factor influencing aggregation is the relative site density of a receptor common to both M and N antigen structures although other nondiscriminating receptor sites on a lower layer of sialic acid are possible also involved.