Chemistry and biology of the anaphylatoxin related serum peptide system. I. Purification, crystallization and properties of classical anaphylatoxin from rat serum

Classical anaphylatoxin, which causes histamine liberation and lethal anaphylatoxin shock in the guinea pig, was purified from dextran‐treated rat serum leading to a 5000‐fold increase in specific activity. It was crystallized in a molecular homogenous state. Rat anaphylatoxin consists of one peptide unit with a molecular weight of 9500, as determined by gel chromatography. First, evidence is presented that the anaphylatoxin‐forming contact reaction of normal, fresh serum with hydrophilic, insoluble substances of high molecular weight, e.g. dextran, yeast or antigen‐antibody complexes, does not lead to a stable anaphylatoxin molecule exclusively, but to a group of peptides of similar physicochemical behavior. Only one of these peptides displays anaphylatoxin activity. The lack of significant chemotactic activity for neutrophil leucocytes is characteristic for this crystallized classical anaphylatoxin. This indicates that anaphylatoxin and chemotactic activities are two different biological principles.