Peptide immunomodulators
This group includes naturally occurring preparations that restore immune system function in various deficiencies.
- Thymus preparations. Used in conditions where the production of endogenous peptide hormones is reduced (due to aging, radiation, or poor environmental conditions). They reduce susceptibility to seasonal infections and normalize immune parameters. The main advantage is extremely rare side effects and allergic reactions.
- Bone marrow preparations. A prominent representative is the domestic complex drug Mielopid. Modern data show that its peptides act predominantly via T-lymphocytes and macrophages, while the effect on B-cells is indirect.
- Transfer factor. Obtained from human leukocyte dialysate. Its feature is that it demonstrates traits of antigenic specificity, although the exact scientific mechanism of this phenomenon remains unexplained.
Preparations of bacterial and microbial origin
Historically, the first immunomodulators were components of microbial cells, such as endotoxins. However, due to high toxicity and uncontrolled polyclonal activation, they had to be abandoned.
Later, combination drugs (Prodigiozan) and vaccines based on Mycobacterium tuberculosis and Corynebacterium parvum began to be used. Their action is based on the presence of PAMPs (pathogen-associated molecular patterns). They powerfully activate the innate immune system, which then triggers an adaptive response.
More modern and safer agents are created based on purified or synthesized components:
- Peptidoglycans. Licopid is a domestic synthetic analogue of a bacterial cell wall fragment. It binds to intracellular NOD receptors of macrophages, enhancing cytokine production and the expression of adhesion molecules and MHC-II. An important property of Licopid: it corrects only altered parameters without affecting normally functioning pathways.
- Nucleic acids. Preparations based on unmethylated CpG sequences (characteristic of microbial DNA) activate TLR-9 receptors. The targets are innate immunity cells, NK cells, and B-lymphocytes.
Synthetic immunomodulators
Many drugs in this group were originally developed to treat completely different diseases, but during clinical practice, they were found to have immunotropic properties.
- Decaris (levamisole). Originally an anthelmintic agent. Capable of increasing T-lymphocyte proliferation and cytokine secretion. Previously actively used in oncology and pulmonology, but today excluded from the arsenal of immunologists due to high toxicity.
- Diucifon. Created as an antileprotic chemotherapeutic drug. Works as a costimulator of IL-2 production by T-lymphocytes. Currently has limited use in burn disease and chronic inflammation.
- Polyoxidonium (azoximer bromide). Selectively acts on macrophages and B-lymphocytes.
Immunosuppressants
To suppress immunity (during transplantation or autoimmune pathologies), chemical immunosuppressants are used.
First generation (cytotoxic agents) These include mercaptopurine, azathioprine, and cyclophosphamide. Being structural analogues of nitrogenous bases, they incorporate into synthesized DNA and kill the cell at the moment of division. Their main drawback is absolute non-selectivity. They destroy not only activated lymphocytes, but also all rapidly dividing healthy cells, causing depletion of lymphoid tissue and severe hematopoietic disorders.
Modern drugs More advanced agents are of natural origin and have a narrow mechanism:
- Cyclosporine. A cyclic decapeptide first isolated from the soil fungus Tolypocladium inflatum.
- Tacrolimus. Isolated from Streptomyces inflatum. Despite chemical differences from cyclosporine, it possesses a very similar mechanism of suppressing immune reactions.
Application and the problem of pseudo-immunomodulators
True immunomodulators are prescribed strictly according to indications in combination with baseline therapy. The main goal is the treatment of secondary immunodeficiencies arising against the background of chronic inflammation, tumors, radiation therapy, trauma, or severe viral and allergic diseases.
It is important to distinguish them from drugs with nonspecific side effects (e.g., dibazole). In addition, vitamins, micronutrients, and adaptogens, although exerting a beneficial effect on the body, cannot be quantitatively assessed as immunomodulators. Aggressive advertising of dietary supplements under the guise of immunotropic agents distorts the understanding of this complex group of drugs.
Briefly: answers to topical questions
What is the molecular mechanism of action of cyclosporine inside the T-lymphocyte?
The molecular mechanism of action of cyclosporine consists in inactivating the enzyme calcineurin and interrupting Ca2+-dependent signal transmission. Stages of intracellular action:
- Binding to the intracellular protein cyclophilin (immunophilin).
- Formation of a complex that inactivates the phosphatase calcineurin.
- Blockade of dephosphorylation of the cytoplasmic transcription factor NF-AT.
- Prevention of NF-AT translocation into the nucleus and binding to target genes.
As a result of these processes, T-cell activation is suppressed, interleukin-2 (IL-2) production is reduced, and the expansion of T-lymphocyte clones is blocked.
Class and exam questions
Why are vitamins and adaptogens not considered immunomodulators?
They exert a general beneficial effect on the body, but have no specific cellular or receptor targets in the immune system, and their effect cannot be accurately quantified.
How does the drug Licopid work?
It binds to intracellular NOD receptors of macrophages, which leads to enhanced cytokine synthesis and increased expression of major histocompatibility complex molecules (MHC-II), while the drug does not affect baseline normal parameters.
Why are first-generation immunosuppressants rarely used now?
Drugs like mercaptopurine and cyclophosphamide block DNA synthesis in any dividing cells. Because of this, they nonspecifically disrupt hematopoiesis, tissue renewal, and cause total suppression of all forms of the immune response.
What else to study on this topic
- Mechanisms of PAMP recognition by innate immunity cells
- The role of NOD receptors and TLR-9 in intracellular signal transduction
- Causes of levamisole toxicity with prolonged use
- Differences in the chemical structure of cyclosporine and tacrolimus
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