Synthesis of an IgG fragment decapeptide exhibiting phagocytosis stimulating activity of polymorphonuclear leucocytes.

Fragment 335-344 of human IgG was synthesized stepwise, using active esters of N-protected amino acids and benzotriazolyloxytris (dimethylamino)phosphonium hexafluorophosphate for coupling. This fragment could be liberated from the carrier molecule by the two specific enzymes responsible for the release of tuftsin from the same carrier molecule: tuftsin endocarboxy-peptidase cleaves at the Arg-Glu bond and leukokininase at the Lys-Thr bond. This decapeptide fragment, Thr-Ile-Ser-Lys-Ala-Lys-Gly-Gln-Pro-Arg showed significant activity in stimulating phagocytosis of human polymorphonuclear leucocytes.