Effects of fibrinogen degradation fragments D and E on cell-mediated immunity

Serum taken from severely traumatized victims suppresses in vitro the response of normal lymphocytes to the mitogenic stimulant phytohemagglutinin (PHA). In the postburn period, fibrin degradation products (fragments D and E) are elevated in a high percentage. Controversy exists as to whether these fragments contribute to what is clinically evident as cell-mediated immune (CMI) suppression. Purified fragments D and E were isolated over an ion exchange cellulose column after activating, with streptokinase, a solution containing fibrinogen and plasminogen. Lymphocytes from six volunteers were cultured with PHA and serial dilutions of fragments D and E; each was analyzed for ability to incorporate radiolabeled thymidine. Fragment E possessed in vitro CMI suppression at pharmacologic doses. Fragment D demonstrated immune suppressive capabilities at doses approximating those estimated to occur in the acute postburn phases of injury.