Injectable bovine collagen has been used clinically for years. But both the necessity of repeated injections to maintain corrections and the question of adverse allergic reactions developing from the use of a xenogenic collagen have been an area of serious concern. To overoome these adverse effects

we have developed injectable collagen preparations from human placenta. Gamma irradiation was used for sterilization and crosslinkins of the collagen.We observed the mouse immune respose to gamma-irradiated human placenta soluble and insoluble collagen following multiple injections. After six injections of these materials

no total IgG level increase was found

nor was antibody specifically directed against human collagen found.Mouse antibody levels were also observed following Zyderm II and Zyplast repetitive injections and following repetitive implantations of coated vicryl and chromic gut. No humoral immune response was found in this heterologous type system.