Classification and origin of drugs
Antibody drugs used as immunosuppressants show considerable diversity. First and foremost, they are categorized by the origin of the protein molecule. In clinical practice, one encounters murine, chimeric, humanized, and fully human antibodies. Animal-derived agents (e.g., rabbit or horse antibodies) are also distinguished.
According to their mechanism of action and key targets, the following main groups are identified:
- TNF-α inhibitors. This group includes etanercept and infliximab, as well as certolizumab pegol, adalimumab, and golimumab. A detailed pharmacological profile of these drugs is usually reviewed under the topic 'Disease-modifying antirheumatic drugs'.
- IL-2 receptor antagonists. Typical representatives are daclizumab and basiliximab.
- Polyclonal antibodies. This group includes antithymocyte globulin.
IL-2 receptor antagonists: focus on basiliximab
Basiliximab is a prominent representative of chimeric monoclonal antibodies. Its molecular structure is combined: it consists of 75% human amino acid sequences and 25% murine peptides. This distinguishes it from fully human or humanized analogs.
In its core pharmacological properties—clinical profile, indications for use, mechanism of immunosuppressive action, and spectrum of adverse effects—basiliximab is completely identical to daclizumab. However, there is one critically important difference between them: the pharmacological activity of basiliximab is exactly 10 times higher than that of daclizumab, making it a more potent tool for targeted therapy.
Polyclonal antibodies: antithymocyte globulin
Antithymocyte globulin (known under the trade name Thymoglobulin) is fundamentally different from monoclonal antibodies. By origin, these are polyclonal rabbit or horse antibodies that specifically bind to human thymocytes.
The drug's mechanism of action represents a sequential cascade of reactions:
- First, antibodies tightly bind to the surface of circulating T-lymphocytes in the blood.
- Then, direct destruction of these lymphocyte cells occurs.
- The resulting fragments of destroyed cells undergo phagocytosis by macrophages in the liver and spleen tissues.
- Conclusion: profound lymphopenia develops, accompanied by a marked impairment of the immune response.
In clinical practice, Thymoglobulin is prescribed to prevent transplant rejection reactions after kidney, heart, liver, or pancreas transplantation. In addition, the drug is effective in the combination treatment of aplastic anemia.
Safety profile and adverse effects
Therapy with immunosuppressive antibodies requires careful monitoring due to a wide range of adverse reactions.
Common side effects include:
- Metabolic disorders: development of hyperlipidemia.
- Gastrointestinal disorders: nausea and diarrhea.
- Hematologic shifts: leukopenia and thrombocytopenia.
- Other reactions: headache and potential nephrotoxicity.
When using Thymoglobulin, fever, serum sickness-like reactions, and skin lesions (erythematous or pustular rashes) are frequently observed. Blood tests reveal not only thrombocytopenia but also neutropenia.
The greatest clinical danger is posed by severe anaphylactoid reactions. They can occur right during the drug infusion or immediately after its completion. A characteristic feature is that these reactions most frequently develop in response to the very first administration. The symptom complex includes a sharp drop in blood pressure, urticarial rash, fever, and severe respiratory distress syndrome ('shock lung' syndrome).
To memorize the mechanism of action of antithymocyte globulin, use the rule 'BRPL': Binding (to T-cells) → Reduction/Destruction → Phagocytosis (in the liver and spleen) → Lymphopenia (conclusion).
Class and exam questions
What is the structural difference between basiliximab and fully human antibodies?
Basiliximab is a chimeric antibody. In its protein structure, 25% of the amino acid sequences are of murine origin, and 75% are human.
When is the risk of developing anaphylactoid reactions during antithymocyte globulin infusion the highest?
Severe reactions, such as a drop in blood pressure and shock lung syndrome, most frequently develop during or immediately after the very first administration of the drug.
What is the ultimate result of antithymocyte globulin action on blood cells?
The drug causes the destruction of circulating T-lymphocytes followed by phagocytosis of their fragments. This leads to marked lymphopenia and profound suppression of the immune response.
What else to study on this topic
- Disease-modifying antirheumatic drugs (TNF-α inhibitors: etanercept, infliximab).
- Pharmacodynamics and full clinical profile of daclizumab.
- Pathogenesis of serum sickness reactions upon administration of foreign animal proteins.
- Emergency care measures for respiratory distress syndrome and anaphylactoid reactions.
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Full study guide on 'Immunosuppressive monoclonal antibodies' and another 5,304 pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the section "Agents Regulating Immune Processes"
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.