The importance of the included serum proteins in the immune response in rabbits to a rat skin xenograft.

Various substances were isolated from rat skin including, protein-dermatan sulfate, certain other species of heavy and light protein-mucopolysaccharides, five electrophoretically separable nonstructural glycoproteins and a crude and two "purified" variants of structural glycoproteins. When the serum proteins contaminating these substances were removed as completely as possible, none of these produced an accelerated immune response to a rat skin graft in appropriately preimmunized rabbits, and none of those that were tested had a blocking effect on the immune response. On the other hand, the contaminated products and undenatured and denatured rat serum produced accelerated immune responses to a rat skin graft in appropriately preimmunized rabbits. These observations, together with those on skin reactions to the isolated products and to rat serum in rabbits sensitized by rat skin grafts, emphasize the importance of the included serum proteins in the immune response to this type of xenograft.