Alloimmunity

Alloimmunity

Illustration of alloimmunity.

Alloimmunity refers to the immune response of an organism against antigens from another individual of the same species. It is a natural defense mechanism that plays a crucial role in protecting the body against foreign substances. However, alloimmunity can also lead to various pathological conditions, such as transplant rejection and autoimmune diseases.

Mechanisms of Alloimmunity

Alloimmunity can be triggered by the recognition of foreign antigens, known as alloantigens, by the immune system. These alloantigens are typically derived from genetic differences between individuals, such as major histocompatibility complex (MHC) molecules. The immune response against alloantigens involves the activation of immune cells, including T cells and B cells, leading to the production of antibodies and the recruitment of other immune cells to eliminate the foreign substances.

Transplant Rejection

Illustration of transplant rejection.

One of the most well-known consequences of alloimmunity is transplant rejection. When an organ or tissue is transplanted from one individual to another, the recipient's immune system recognizes the alloantigens present on the transplanted tissue as foreign and mounts an immune response against them. This immune response can lead to the destruction of the transplanted organ or tissue, ultimately resulting in transplant failure.

To prevent transplant rejection, various immunosuppressive strategies are employed, such as the use of immunosuppressive drugs and matching the donor and recipient for compatible MHC molecules. However, despite these measures, alloimmunity remains a significant challenge in the field of transplantation.

Autoimmune Diseases

Alloimmunity can also contribute to the development of autoimmune diseases. In autoimmune diseases, the immune system mistakenly targets and attacks the body's own cells and tissues. This can occur when the immune system fails to distinguish between self and non-self antigens, leading to the production of autoantibodies and the activation of autoreactive immune cells.

The exact mechanisms underlying the development of autoimmune diseases are complex and multifactorial. However, alloimmunity has been implicated in certain autoimmune conditions, such as rheumatoid arthritis and systemic lupus erythematosus. In these diseases, the presence of alloantigens or molecular mimicry between self and foreign antigens can trigger an immune response, leading to chronic inflammation and tissue damage.

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See Also

• Immune system
• Major histocompatibility complex
• Transplantation
• Autoimmune diseases

References

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