ELISA validation. (A) The coating antibody binds equally to Met-α2AP (▴, solid line) and Asn-α2AP (■, dashed line), as shown by detection with HRP-conjugated rabbit anti–human α2AP. In both the total α2AP antigen ELISA (B) and the C-terminally intact α2AP antigen ELISA (C), the absorbance of pooled normal plasma (■, solid line) was completely lost after the addition of a 5× (●, dotted line) or a 10× (▴, dashed line) excess of plasmin. Recovery plots for both the total α2AP antigen ELISA (D) and the C-terminally intact α2AP antigen ELISA (E) show good recovery of purified α2AP added to α2AP-depleted plasma (●, dotted line) compared with purified α2AP only (■, solid line). α2AP-depleted plasma (▴, dashed line) did not respond in either ELISA.