Transplantation is a method of treating the patient with malfunctioned organ or tissue with the healthy one. The organ to be taken is called graft from a healthy individual referred as donor . The individual who receives the graft is called recipient . The transplantation is called orthotropic if the graft is used for an identical anatomical position and heterotropic if used in a different anatomical location. The blood from one individual can be transferred to another individual of same blood group and the process is called as transfusion . The method of transplantation can turn into rejection if the graft belongs to a genetically different individual. The phenomenon of rejection is a large and one of the challenging areas of research in the field of immunology. The immunology behind a tissue or cell rejection is due to the adaptive immune response. One major concept to remember here is an inbred strain of animal is genetically identical because of the homozygous nature of all the genes except the sex chromosome.

 

A graft transplanted from one part of body to other of a same individual is called autologous graft .

A graft transplanted from one individual to a genetically identical individual is called syngeneic graft .

A graft transplanted from one individual to a genetically different individual is called allogeneic graft (allograft) .

A graft transplanted between individuals of two different species is called xenogeneic graft (xenograft) .

The substances recognized as foreign by the host immune system in an allograft are called alloantigens and the lymphocytes and antibody against those are called alloreactive . Similarly, for xenograft the substances are called xenoantigens and counteracting immunity is called xenoreactive .