The immune system protects the body from infections and foreign substances. Sometimes, however, it may become overactive (as in autoimmune diseases) or needs to be intentionally suppressed (such as after an organ transplant). In other cases, patients may need medicines to boost the immune response, especially when immunity is weak. Drugs that decrease immune activity are called immunosuppressants, and drugs that increase immunity are known as immunostimulants.
IMMUNOSUPPRESSANTS
These drugs are used to prevent the body from rejecting transplanted organs and to control autoimmune diseases. They work by reducing the activity of immune cells, especially T-cells.
Main Uses
- Organ transplant (kidney, liver, heart)
- Autoimmune diseases (rheumatoid arthritis, psoriasis)
- Inflammatory bowel disease (Crohn’s disease, ulcerative colitis)
Major Classes of Immunosuppressants
1. Calcineurin Inhibitors
These are the most widely used transplant drugs. They block T-cell activation by inhibiting an enzyme called calcineurin.
a. Cyclosporine
One of the first major immunosuppressants used in transplant therapy.
- Uses: Organ transplantation, rheumatoid arthritis, psoriasis
- Side effects: Kidney toxicity, gum overgrowth, high blood pressure
b. Tacrolimus
More potent than cyclosporine.
- Uses: Organ transplant prevention of rejection
- Side effects: Kidney toxicity, tremors, increased blood sugar
2. Antimetabolites
These drugs interfere with DNA synthesis in immune cells and suppress their multiplication.
a. Azathioprine
- Uses: Transplantation, autoimmune disorders
- Side effects: Bone marrow suppression, liver problems
b. Mycophenolate mofetil (MMF)
- Uses: Often combined with calcineurin inhibitors
- Side effects: Diarrhoea, low blood counts
3. mTOR Inhibitors
These block a key enzyme (mTOR) needed for T-cell growth.
a. Sirolimus (Rapamycin)
- Uses: Kidney transplant
- Side effects: High cholesterol, delayed wound healing
4. Glucocorticoids (Steroids)
These drugs suppress inflammation and immune activity.
- Prednisolone
- Dexamethasone
Side Effects
- Weight gain
- High blood sugar
- Weak bones
- Increased infection risk
5. Biological Agents (Monoclonal Antibodies)
These are targeted therapies that block specific immune pathways.
- Infliximab – blocks TNF-alpha
- Rituximab – targets B-cells
- Basiliximab – prevents transplant rejection
Side Effects of Immunosuppressants (General)
- Increased risk of infections
- Higher risk of cancer (due to reduced immune surveillance)
- Kidney and liver damage (drug-specific)
- High blood pressure
- Gastrointestinal upset
IMMUNOSTIMULANTS
These are drugs or biological substances that boost immunity. They are used when the immune system is weak or when enhanced defence is needed.
Main Uses
- Certain viral infections
- Cancers
- Immunodeficiency conditions
- As vaccines or vaccine adjuvants
Major Classes of Immunostimulants
1. Interferons
Natural proteins that boost antiviral and immune responses.
- Uses: Hepatitis B & C, some cancers, viral infections
- Side effects: Flu-like symptoms, fatigue
2. Interleukins
Help activate immune cells like T-cells and natural killer cells.
- IL-2: used in kidney cancer and melanoma
3. Thymic Hormones
Support T-cell development.
- Thymosin
4. Colony-Stimulating Factors (CSFs)
These medicines increase blood cell production, especially after chemotherapy.
- G-CSF (Filgrastim)
- GM-CSF
Uses
- Boost white blood cells
- Prevent infections in cancer patients
Vaccines as Immunostimulants
Vaccines are one of the most effective immunostimulants. They train the immune system to recognize and fight infections.
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