Types of Organ Rejection

Study Notes

Hyperacute rejection: occurs immediately within minutes to hours, caused by preformed antidonor antibodies (anti ABO blood group antibodies, anti HLA antibodies)
Acute rejection: occurs within days, weeks, or months, caused by acute cellular rejection and acute humoral rejection
Chronic rejection: occurs within months to years, cause unclear, involves antibodies, immune complexes, and slow cellular reaction

Hyperacute rejection: abrupt onset of oliguria, may be associated with fever and graft tenderness
Acute rejection: clinical presentation varies
Chronic rejection: pathogenesis involves T cells inducing monocyte/macrophage infiltration into the graft, along with endothelial cells to produce growth factors and cytokines (PDGF, Insulin-like growth factor, epidermal growth factor, IL-1, IL-6, TNF, and TGFβ)

Screening of recipient and donor for blood group matches
Tissue matching: donor and recipient share the same MHC class I and class II antigens
Immunosuppressive therapy

Primary immunodeficiency: congenital and hereditary, patient born with a genetic mutation that results in a defect in either the innate or adaptive immune response
Secondary immunodeficiency: acquired on a transient or permanent basis, examples include SLE (which affects women about 10 times more frequently than men) and injury

Histocompatibility antigens determine rejection between two genetically different individuals
Major histocompatibility complex (MHC class I and II molecules) cause strong, rapid responses, principally responsible for transplant rejection
Types of graft: xenograft, allograft, isograft, and autograft
Mechanism of graft rejection: cellular rejection (T cell mediated) and humoral rejection (antibody mediated)

Immune system reacts to an enormous variety of microbes but does not react against individual's own (self) antigens
Unresponsiveness to antigens is called immunological tolerance
Inability to respond to antigen stimulation or immunological unresponsiveness is tolerance
Failure of tolerance mechanisms leads to autoimmunity or autoimmune disease
Tolerance: central tolerance (inactivation or destruction of lymphocytes during early development) and peripheral tolerance (inactivation or destruction of mature lymphocytes in peripheral tissues)
Autoimmune disease: immune response against self-antigens as a result of breakdown of tolerance, can be either systemic or organ-specific
Factors influencing autoimmune diseases: genetic (MHC alleles, non-MHC genes, FcgR, Fas/FasL), environmental (microbes), and gender (hormones play a role)