Collagen grafts--here today and gone tomorrow.

The ongoing search for the perfect graft to fill out facial contour defects has frustrated reconstructive surgeons for years. The list of autogenous, homologous, heterologous, and alloplastic materials is extensive. All implantable materials have one or more classical principal drawbacks: shrinkage, extrusion, infection, absorption, and/or deformation. One of the major mechanisms of graft unacceptability is the phenomenon of tissue immunity and graft rejection. This has traditionally been the major disadvantage of homografts and heterografts. The host's immune system recognizes the implant as "non-self," an antibody-antigen reaction is triggered--usually by the antigenic stimulation provided by the proteinaceous component of the graft, and the implant is rejected or destroyed. Conversely, autogenous grafts experience the problem of resorption by the action of macrophages and chronic inflammatory cells. The immunologic sterility of alloplastic grafts is an advantage, but the body often rejects even the most inert materials by the process of chronic inflammation.