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 phagocytosis^3,4 and in clearing bacteria from the blood stream^2,5. Also, F(ab′)₂ fragments are non-cytotoxic in the presence of complement^6,7 and enhance the growth of tumours^8,9. Because severely burned patients have larger than normal concentrations of proteolytic enzymes¹⁰ and immunoglobulins in their serum^11–13, 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.