IMMUNOLOGICAL DISCRIMINATION OF DIVERSE FORMS OF HUMAN ALPHA(1)-PROTEINASE INHIBITOR

The immunodiffusion cross-reactivity and competitive inhibition ELISA assays were used for immunological differentiation of latent form, cle aved farm and guanidinium hydrochloride (GuHCl) induced polymer of hum an alpha(1)-proteinase inhibitor (alpha(1)-PI). Under the conditions s tudied, the differences between latent form and GuHCl-induced polymers of the inhibitor in terms of immunological response were estimated to amount to about 30% and differences between latent and cleaved alpha( 1)-PI to about 50%. The immunodiffusion and ELISA data for citrate-ind uced polymers suggest that in their structure the latent molecule is i nvolved. On the basis of competitive inhibition data, we suggest that the alpha(1)-PI protein polymerisation involves insertion of the react ive-site loop (RSL) into the A-sheet under mild conditions and that in the latent form of the inhibitor RSL is incompletely inserted into th e A-sheet.