Alloimmunity

An immune response to non-self antigens from the same species

Alloimmunity
Synonyms	Alloimmune response, Alloreactivity
Pronounce	N/A
Specialty	N/A
Symptoms	Rejection of transplanted organs, hemolytic disease of the newborn
Complications	Graft-versus-host disease
Onset
Duration
Types	N/A
Causes	Immune response to alloantigens
Risks	Organ transplantation, blood transfusion, pregnancy
Diagnosis
Differential diagnosis	N/A
Prevention	N/A
Treatment	Immunosuppressive therapy
Medication	N/A
Prognosis
Frequency
Deaths	N/A

Alloimmunity, also known as alloreactivity, is an immune response that occurs when the immune system of an individual reacts against antigens from another individual of the same species. These antigens, known as alloantigens, can be present on cells or tissues that are introduced into the body through processes such as organ transplantation, blood transfusion, or during pregnancy.

Mechanism

Alloimmunity is primarily mediated by T cells and B cells of the immune system. When alloantigens are recognized as foreign, the immune system mounts a response to eliminate them. This can lead to the destruction of transplanted organs or tissues, a process known as graft rejection.

There are two main types of alloimmune responses:

• Direct allorecognition: This occurs when recipient T cells directly recognize donor major histocompatibility complex (MHC) molecules on the surface of donor cells.
• Indirect allorecognition: This occurs when recipient antigen-presenting cells process donor antigens and present them to T cells, which then mount an immune response.

Clinical Manifestations

Alloimmunity can manifest in several clinical scenarios:

• Transplant rejection: The immune system attacks a transplanted organ or tissue, leading to its failure. This can be acute or chronic.
• Graft-versus-host disease (GVHD): Occurs when donor immune cells attack the recipient's tissues, commonly seen in bone marrow transplantation.
• Hemolytic disease of the newborn: Occurs when maternal antibodies target fetal red blood cells, often due to Rh incompatibility.

Management

The management of alloimmunity involves the use of immunosuppressive drugs to reduce the immune response and prevent rejection. Commonly used drugs include cyclosporine, tacrolimus, and corticosteroids.

Research and Future Directions

Research in alloimmunity is focused on improving the outcomes of organ transplantation and developing strategies to induce tolerance to alloantigens. This includes the use of regulatory T cells and gene therapy approaches.

Also see

• Immunology
• Autoimmunity
• Transplantation immunology
• Blood transfusion
• Pregnancy and the immune system