Factors influencing bonding of bromelain agglutinators and their Fab fragments.

The complex of bromelain agglutinators and their homologous Fab fragments is dissociated by gel chromatography under certain conditions. When albumin is present as a source of thiol groups, Fab fragments previously treated with N-ethylmaleimide (NEM) will dissociate from the agglutinators (fluid phase). If anti-Rh Fab fragments are bound to Rh-positive erythrocytes, the agglutinates are not dissociated by thiols (cellular phase). Prior to erythrocyte sensitization, the agglutinator site on Fab fragments can be blocked by thiol-disulfide exchange. Once the Fab fragments are coated on erythrocytes, the agglutinator site is more readily available than it was prior to sensitization, as evidenced by inhibition with 0.01 M NEM. The differences between the bonding characteristics of the fluid phase and the cellular phase and the influence of mercaptoalbumin on the agglutinator-Fab complex suggest that the agglutinators are not antibodies.