The greatest chance for long-term survival of an allograft would be expected with a

Of the grafts listed, cornea transplants have the longest survival time. Cells of the cornea do express HLA-A and HLA-B antigens, but their density is low compared with most other tissues. In addition, the cornea is considered to be an "immunologically privileged" site (i.e., blood vessels and lymphatics are lacking).There appears co be little or no interaction between corneal proteins and cells of the immune system.HLA matching of donor and recipient is generally not done before cornea transplants. Topical and subconjunctival steroids are the conventional forms of immunosuppressive therapy used.Other sites and tissues considered to be "immunologically privileged" include the brain, testes, and uterus.As with most other types of allografts, rejection (if it is going to occur) of a transplanted cornea occurs most frequently during the first 3 to 6 months after transplantation.A high success rate is also seen with bone allografts. Bone is often frozen or freeze-dried before transplantation. These procedures reduce its immunogenicity.There are a few long-term survivors of kidney, hea, liver, and pancreas transplants, but the overall success rates are considerably lower than for cornea transplant patients.