Some of the earliest attempts to replace damaged tissues by transplantation were during World War II as a way of treating pilots who had received severe skin burns in airplane crashes. It was soon realized that individuals reject tissue grafts from other individuals. Rejection results from inflammatory reactions that damage the transplanted tissues. Studies since the 1940s and 1950s established that graft rejection is mediated by the adaptive immune system because it shows specificity and memory and it is dependent on lymphocytes (Fig. 1). Much of the knowledge about the immunology of transplantation came from experiments with inbred strains of rodents, particularly mice. All members of an inbred strain are genetically identical to one another and different from the members of other strains. The experimental studies showed that grafts among members of one inbred strain are accepted and grafts from one strain to another are rejected, firmly establishing rejection as a process controlled by the animals’ genes. Later experiments defined the nature of the genes that control graft rejection and showed that the products of many of these genes are expressed in all tissues.

Fig1. Evidence indicating that the rejection of tissue transplants is an immune reaction. Clinical and experimental evidence indicates that rejection of grafts is a reaction of the adaptive immune system. MHC, Major histocompatibility complex.

As mentioned in Chapter 3, the genes that contributed the most to the rejection of grafts exchanged between mice of different inbred strains are called major histocompatibility complex (MHC) genes. The language of transplantation immunology evolved from the experimental studies. The individual who provides the graft is called the donor, and the individual in whom the graft is placed is the recipient or host. Animals that are identical to one another (and grafts exchanged among these animals) are said to be syngeneic; animals (and grafts) of one species that differ from other animals of the same species are said to be allogeneic; and animals (and grafts) of different species are xenogeneic. Allogeneic and xenogeneic grafts, also called allografts and xenografts, are always rejected by a recipient with a normal immune system. The antigens that serve as the targets of rejection are called alloantigens and xenoantigens, and the antibodies and T cells that react to these anti gens are alloreactive and xenoreactive, respectively. In the clinical situation, transplants are exchanged between allogeneic individuals who are members of an outbred species who differ from one another (except for identical twins). Most of the following discussion focuses on immune responses to allografts.

مواضيع ذات صلة

Immune Mechanisms of Graft Rejection

Induction of Immune Responses Against Transplants

Transplantation Antigens

Glycans and Immunity

Cancer Immunotherapy : Stimulation of Host Antitumor Immune Responses by Vaccination With Tumor Antigens

Cancer Immunotherapy: Immune Checkpoint Blockade

Cancer Immunotherapy: Adoptive T Cell Therapy

Cancer Immunotherapy: Passive Immunotherapy With Monoclonal Antibodies

Evasion of Immune Responses by Tumors

PROCESS OF PHAGOCYTOSIS

GRANULOCYTIC CELLS

B Cell Epitope Binding Predictions