A SERUM AGGLUTININ INHIBITED BY IONIZED CALCIUM

Summary. Experiments have been carried out to determine the reactions and nature of a serum property which will agglutinate erythrocytes only when ionized calcium is absent from the reacting mixture. The agglutinin has the specificity of anti‐H, and appears to be a 19 S γM globulin. The calcium ion itself seems to be the inhibitory factor and presumably combines with the agglutinin molecule at its erythrocyte binding sites, but can be removed by the addition of salts which have the ability to chelate calcium. © 1969 Blackwell Publishing Ltd