Hemagglutination enhancement by bovine serum albumin is affected by octanoate, Reactive Blue 2 (Cibacron Blue), and polymer

An AutoAnalyzer system was used to study factors that influence the albumin enhancement of agglutination of Rh(D)-positive red cells by IgG anti-D. An albumin consisting of trimer and higher oligomer was more efficient than a preparation composed mainly of monomer and dimer. Modification of the hemagglutination-enhancing property of albumin was obtained by the addition of ligands (octanoate [caprylate] and Reactive Blue 2 [Cibacron Blue]). Irrespective of the polymer content, neither ligand alone had any effect on low-fatty-acid albumins. However, when mixtures of octanoate and Cibacron Blue were added to the same albumins, hemagglutination was initially increased, and then diminished with increasing concentrations of ligands. The enhancing property of high-fatty-acid, nonpolymerized albumin was markedly reduced by the addition of octanoate or Cibacron Blue. On the other hand, only Cibacron Blue could produce the same inhibitory effect on a polymerized albumin with high fatty acid content. The implication is that the total free fatty acids bound and polymer content are two independent variables that can affect the performance of an albumin as a hemagglutination enhancer.