Circulating Mediators in Thermal Injuries: Isolation and Characterization of a Burn Injury-Induced Immunosuppressive Serum Component

Abstract

Immunosuppression in thermally injured patients is a well-documented phenomenon that significantly contributes to the high incidence of septic episodes. This report reviews the isolation and partial characterization of a burn injury-induced suppressor active peptide (SAP) that is believed to play a critical role in immunosuppression following thermal trauma. This SAP complex appears to be a prostanoid carrier complex with the following characteristics: (1) a low molecular weight (between 1,000 and 5,000); (2) a complex composition containing a protein component rich in glycine and serine, a carbohydrate moiety containing sialic acid, and a lipid component (which apparently includes arachidonic acid metabolites); (3) a structure that is heat stable (56 C for 30 minutes), pH stable, and unaffected by treatment with tryp-sin, proteinase K, DNAse, and RNAse; (4) a suppressive mode of action that is dependent on the presence of the lipid moiety (most likely PGE2 since treatment with anti-PGE2 often blocks activity and activity can be restored to the delipidated molecule by reintroduction of PGE2); (5) a noncytotoxic immunosuppressive mode of action; and (6) erythrocyte hemolytic capability that is dependent upon the sialo-peptide component (delipidation does not affect hemolytic activity).