last updated 21-11-2024

Anti-thymocyte globulin (ATG)

Anti-thymocyte globulin (ATG)

ATG or thymoglobulin is a polyclonal rabbit-derived antibody against human T cells which is used in the prevention and treatment of acute rejection in organ transplantation.

The presumed mode of action of ATG is via selective depletion of T-cells by complement-dependent lysis. The exact mechanism by which polyclonal anti-lymphocyte preparations suppress immune responses is not fully understood. Possible mechanisms by which thymoglobulin may induce immunosuppression in vivo include: T-cell clearance from the circulation and modulation of T-cell activation and cytotoxic activities. Thymoglobulin includes antibodies against T-cell markers such as CD2, CD3, CD4, CD8, CD11a, CD18, CD25, CD44, CD45, HLA-DR, HLA Class I heavy chains.

ATG can be administered at the time of the transplant to prevent rejection, or used as reserve for the treatment of steroid-resistant acute rejection. In patients, T-cell depletion is usually observed within a day from initiating therapy.

ATG is associated with a large number of adverse effects of which cytokine release syndrome and increased risk of post-transplant lymphoproliferative disorder are serious. Symptoms include fever, chills, pain, headache, abdominal pain, diarrhea, and nausea. Anaphylaxis can occur within 3 days after infusion (symptoms: fever, erythema, edema, hypotension). Leukopenia and trombocytopenia are related with cross-reactions with the antibodies. Due to over-immunosuppression patients can develop diverse infections. During therapy, monitoring the lymphocyte count may help assess the degree of T-cell depletion.

Anti-lymphocyte globulin (ALG) is a horse-derived antibody against human T cells which is used in the treatment of acute rejection in organ transplantation, especially in kidney transplants.It is less commonly used than the similar ATG, and like ATG it is associated with cytokine release syndrome in the short term and an increased risk of post-transplant lymphoproliferative disorder in the long term.

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Thymoglobulin acts via 

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