Immunochemistry of Synthetic Polypeptides and Polypeptidyl Proteins

Abstract

Summary One polyglutamic acid, a polylysine, and a multichain polypeptide caused the formation of antibodies in rabbits which would not precipitate the homologous polypeptide but did form precipitates with bovine albumin, fibrinogen, and a few other naturally occurring proteins. The reactions between the modified proteins and antibodies appeared to be especially sensitive to salt concentration—precipitation being more easily inhibited by high salt concentration than the precipitins of many natural proteins. With a few other polyglutamic acid preparations, specific precipitates were formed with their antisera when the ionic strength was lowered to 0.05, suggesting that physiologic saline may have prevented the precipitin formation. The rabbit antisera to polyglutamic acid and the multichain polypeptide caused only a weak anaphylactic reaction in guinea pigs when the challenging antigen was the homologous or similar polypeptide and caused a moderate to fatal anaphylactic shock in guinea pigs challenged with bovine albumin or polyglutamyl bovine albumin. The synthetic polypeptides did not inhibit the reactions between their antisera and the proteins when tested by inhibition of precipitation techniques and passive anaphylaxis. No evidence of a strong reaction between the polypeptides and antisera to similarly modified proteins was found in inhibition of precipitation methods and passive anaphylaxis. Incomplete antibodies were not detected in antisera to polyglutamic acids which did not contain precipitating antibodies. A complex between the multichain polypeptide and its antiserum was not detected in electrophoresis and ultracentrifugal experiments.