Reversal of SAP-induced immunosuppression and SAP detection by a monoclonal antibody

Abstract

A murine monoclonal IgG antibody (MAb) to column-isolated trauma-induced suppressor active peptide (SAP) was produced and utilized in these studies for the further characterization of SAP. Specificity of the antibody was confirmed by enzyme-linked immunosorbent assay (ELISA), passive immunoblotting, and reversal of SAP-induced neutrophil chemotaxis inhibition. ELISA analysis revealed binding of anti-SAP MAb to a serum protein present in both whole burn and normal serum, but only to burn serum using a less than 25,000-mw serum fraction. This suggests that SAP may be an injury-induced degradation product of a greater than 25,000-mw serum protein. Immunoblotting using a less than 25,000-mw burn serum fraction demonstrated MAb binding to a single low molecular weight protein band. Using the MAb in an ELISA immunodiagnostic procedure, it appeared that SAP levels were significantly elevated in the sera of burned patients who died from their injuries compared to levels in sera of controls or patients who survived.