F(ab')2-like fragments from severely burned patients provide a new serum immunoglobin component.

Abstract

INTEREST in immunoglobulin fragments in serum centres around their antigenic sites which stimulate autoantibody1, and the insight they provide into the metabolism of immunoglobulins. They also have the potential to alter host immune defence mechanisms. For example, the F(ab′)2 fragment prepared in vitro from IgG is less effective than intact IgG in protecting animals injected with pathogens2, in aiding phagocytosis3,4 and in clearing bacteria from the blood stream2,5. Also, F(ab′)2 fragments are non-cytotoxic in the presence of complement6,7 and enhance the growth of tumours8,9. Because severely burned patients have larger than normal concentrations of proteolytic enzymes10 and immunoglobulins in their serum11–13, we regarded them as potential models for in vivo degradation of immunoglobulin, and examined serum from forty patients with 3–70 per cent body surface area full-thickness burns for immunoglobulin fragments. The following report identifies for the first time a serum F(ab′)2-like fragment in severely burned patients.