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Monday, August 11, 2025

Immunologic agents


1. Definition and Overview

  • Pharmacological and biological agents that modulate the immune system’s activity.

  • May stimulate (immunostimulants) or suppress (immunosuppressants) immune responses.

  • Includes vaccines, immunoglobulins, monoclonal antibodies, cytokines, immune checkpoint modulators, adjuvants, and related products.

  • Widely used in infection prevention, autoimmune diseases, cancer therapy, transplant medicine, and immune deficiency disorders.

2. Main Categories

A. Immunostimulants

  • Enhance immune system activity.

  • Includes: cytokines (interleukins, interferons), colony-stimulating factors, bacterial derivatives (e.g., BCG), immune adjuvants, checkpoint inhibitors.

B. Immunosuppressants

  • Reduce or inhibit immune activity.

  • Includes: corticosteroids, calcineurin inhibitors (cyclosporine, tacrolimus), mTOR inhibitors (sirolimus, everolimus), cytotoxic agents (azathioprine, cyclophosphamide), monoclonal antibodies against immune cell targets.

C. Passive Immunotherapy

  • Provides immediate immunity via exogenous antibodies.

  • Includes: human immunoglobulin preparations (IVIG, hyperimmune globulins), monoclonal antibodies for infections (palivizumab, bezlotoxumab).

D. Active Immunization

  • Stimulates the body to produce its own antibodies and immune memory.

  • Includes: live attenuated vaccines, inactivated vaccines, subunit vaccines, conjugate vaccines, mRNA vaccines, viral vector vaccines.

E. Immune Modulators

  • Drugs that fine-tune immune responses without complete suppression or overactivation.

  • Includes: thalidomide derivatives, toll-like receptor agonists, certain biological response modifiers.

3. Mechanisms of Action – Core Pathways

  • Antigen presentation enhancement – promotes immune recognition of pathogens or tumor cells.

  • Cytokine signaling modulation – alters the balance between pro-inflammatory and anti-inflammatory signals.

  • Lymphocyte activation/inhibition – controls T-cell and B-cell activity via surface receptors or intracellular pathways.

  • Checkpoint regulation – PD-1, PD-L1, CTLA-4 blockade to enhance T-cell function.

  • Humoral immunity augmentation – increases antibody production and affinity maturation.

  • Cell-mediated immunity control – modifies cytotoxic T-cell, NK cell, and macrophage activity.

4. Therapeutic Applications

Infectious Disease Prevention

  • Vaccines for bacterial and viral pathogens.

  • Passive immunization with immunoglobulins for post-exposure prophylaxis.

Cancer Therapy

  • Immune checkpoint inhibitors, cytokine therapy, cancer vaccines.

  • Monoclonal antibodies targeting tumor-specific antigens.

Autoimmune Diseases

  • Immunosuppressants to control excessive immune activity.

  • Biologicals targeting inflammatory cytokines (e.g., TNF-alpha inhibitors, IL-6 blockers).

Transplant Medicine

  • Immunosuppressive regimens to prevent graft rejection.

  • Monoclonal antibodies for induction therapy.

Primary and Secondary Immunodeficiency

  • Immunoglobulin replacement therapy.

  • Immunostimulants for infection prevention.

5. Examples by Class

Immunostimulants

  • Aldesleukin (IL-2), interferon alfa/beta/gamma, imiquimod, GM-CSF, BCG vaccine, pembrolizumab (PD-1 inhibitor).

Immunosuppressants

  • Cyclosporine, tacrolimus, sirolimus, mycophenolate mofetil, corticosteroids, basiliximab (IL-2R antagonist).

Vaccines

  • Live: measles, mumps, rubella (MMR), yellow fever.

  • Inactivated: polio (IPV), hepatitis A.

  • Subunit: hepatitis B, HPV.

  • mRNA: COVID-19 (Pfizer-BioNTech, Moderna).

  • Viral vector: Ebola, COVID-19 (AstraZeneca, J&J).

Immunoglobulins

  • IVIG, anti-Rh(D) immune globulin, hepatitis B immune globulin, rabies immune globulin.

Cytokines

  • Filgrastim (G-CSF), sargramostim (GM-CSF), interferon beta-1a for multiple sclerosis.

6. Contraindications – General

  • Hypersensitivity to active ingredient or excipients.

  • Live vaccines in immunocompromised individuals.

  • Uncontrolled infections before starting immunosuppressants.

  • Pregnancy restrictions for certain teratogenic agents (e.g., thalidomide, mycophenolate).

7. Adverse Effects – Common Patterns

Immunostimulants

  • Autoimmune disease flare-ups, cytokine release syndrome, flu-like symptoms, skin reactions.

Immunosuppressants

  • Increased risk of infections, malignancy risk, organ toxicity (nephrotoxicity, hepatotoxicity), metabolic disturbances.

Vaccines

  • Local site reactions, mild fever, rare severe allergic responses, rare neurologic events.

Immunoglobulins

  • Infusion reactions, headache, thromboembolic events, renal impairment (rare).

8. Drug Interactions – Common Considerations

  • Immunosuppressants combined → additive infection risk.

  • Live vaccines ineffective or unsafe with concurrent immunosuppression.

  • Cytokines with other immune-activating drugs → higher toxicity.

  • Drugs affecting renal or hepatic metabolism may alter biological drug clearance.

9. Monitoring Requirements

  • CBC with differential – for cytopenia or leukocytosis detection.

  • Liver and kidney function tests – for hepatotoxic or nephrotoxic drugs.

  • Immune function tests – CD4 counts, antibody titers.

  • Disease activity markers – CRP, ESR, autoantibody levels.

  • Infection screening – TB, hepatitis, HIV before initiating immunosuppressive biologics.

10. Clinical Use Strategies

  • Tailored regimens based on disease type, immune status, and comorbidities.

  • Risk–benefit assessment before immune activation or suppression.

  • Pre-treatment screening for latent infections in immunosuppressive therapy.

  • Use combination therapy in cancer or transplant medicine to balance efficacy and toxicity.




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