Connective tissue responses to altered collagen and bone implants

The ϵ‐amino groups of reconstituted collagen were treated in a variety of ways and the collagen implanted subcutaneously in rats. After two weeks the implants were removed and examined histologically. A giant cell response was seen around the collagens treated with 1‐fluoro‐2,4‐dinitrobenzene, p‐nitrobenzoylchloride or carbobenzoxychloride, but not with the other reagents. Parallel experiments with autogenous bone, treated with the same methods, were carried out. A mild giant cell response was found in the untreated bone, but was enchanced only in bone treated with the same three reagents. It would appear that the giant cell response was greatly increased when the attached benzene ring had nitro groups in the para position, and also when there was an ester linkage in the attached radicle. It is unlikely that this reaction was immunological in character. The giant cells have many of the properties of osteoclasts. It is suggested that it is the nature of the organic matrix of bone that determines if osteoclasis shall occur.