X. TRANSPLANT IMMUNOLOGY

Transfer of tissue from one site to another within an individual

Autograft

Transfer of tissue between genetically identical individuals

Isograft (syngraft):

Transfer of tissue between two genetically nonidentical individuals of the same species

Allograft:

Transfer of tissue between two individuals of different species

Xenograft:

occurs when revascularization and healing lead to a repaired site in about 2 weeks.

Graft acceptance

• The first time a graft is encountered, the immune systemmattacks and ultimately destroys (rejects) the nonself tissue.

• This occurs 10–14 days after transplantation.

First-set rejection

The second time nonself tissue with the same or similar antigens is encountered, it is rejected within 6 days.

Second-set rejection

• Occurs within 24 hours of transplantation.

• The rejection is caused by a preexisting antibody to antigens on the grafted tissue.

• The tissue never becomes vascularized.

Hyperacute rejection

What causes hyperacute rejection?

ABO blood group antibodies and MHC class I antibodies

occurs within weeks of transplantation, the rejection is usually due to a CMI response;

Acute rejection

Acute rejection

• Histopathology reveals massive infiltration of ____ and ____

• ____ to vessel walls activating ____ can also trigger acute rejection.

• lymphocytes and macrophages.

• Antibody ; complement

occurs months to years after transplantation;

chronic rejection

The mechanism of Chronic rejection includes

both HMI and CMI.

Chronic rejection is characterized by progressive ____ and scarring of ___ due to proliferation of ____

fibrosis ; blood vessels ; smooth muscle