What are the effects and uses of interferon (Immune system protein) in the body?

Effects and Uses of Interferon in the Body

Interferons are naturally occurring proteins with antiviral, immunomodulatory, and antiproliferative properties that have significant therapeutic applications but also cause numerous side effects that can limit their clinical utility. 1

Mechanism of Action

Interferons are classified into three main types based on their antigenic specificities:

• Alpha (α) interferon: Produced by leukocytes infected with viruses
• Beta (β) interferon: Produced by fibroblasts infected with viruses
• Gamma (γ) interferon: Produced by lymphocytes stimulated with antigens or mitogens 2

Interferons exert their effects through multiple mechanisms:

• Antiviral effects:

  • Inhibition of viral replication
  • Inactivation of viral RNA
  • Inhibition of protein synthesis
  • Prevention of viral maturation and release from infected cells 1, 3

• Immunomodulatory effects:

  • Enhancement of macrophage activity
  • Increased cytotoxic T cell function
  • Stimulation of natural killer (NK) cell activity
  • Enhancement of phagocytic mechanisms 3, 1

• Antiproliferative effects:

  • Inhibition of cell growth
  • Cell differentiation-inducing activity 2

Therapeutic Applications

1. Viral Infections

• Hepatitis C: Historically a cornerstone of treatment, often combined with ribavirin 4

  • Various regimens based on genotype, with sustained virological response (SVR) rates varying by treatment protocol
  • Now largely replaced by direct-acting antivirals in many countries

• Hepatitis B: Used for chronic infection 2

• Other viral infections: Varicella-zoster virus, cytomegalovirus (limited benefit) 3

2. Malignancies

• Hematological malignancies: Multiple myeloma, chronic myelogenous leukemia, malignant lymphoma
• Solid tumors: Renal cell carcinoma, malignant melanoma, glioblastoma, skin cancers 2

3. Multiple Sclerosis

• Interferon beta is a standard treatment for relapsing-remitting multiple sclerosis 5

Side Effects and Adverse Reactions

Approximately 75% of patients treated with interferon experience one or more side effects 4:

Common Side Effects

• Flu-like symptoms (most common):

  • Fever, chills, muscle aches
  • Fatigue, headaches
  • These symptoms typically occur 6-8 hours after injection and often improve after 2-4 weeks of treatment 4

• Hematological effects:

  • Neutropenia
  • Thrombocytopenia
  • Anemia (particularly when combined with ribavirin) 4, 6

• Neuropsychiatric effects:

  • Depression (occurs in approximately 50% of patients)
  • Irritability, anxiety
  • Impaired concentration and memory disturbances
  • Insomnia 4, 7

• Dermatological reactions:

  • Skin irritation at injection sites
  • Erythema, xerosis (dry skin), pruritus
  • Eczematous dermatitis 4

Serious Adverse Effects

• Severe neuropsychiatric effects:

  • Major depression
  • Paranoia, severe anxiety
  • Psychosis
  • Suicidal ideation 4, 7

• Autoimmune disorders:

  • Thyroid dysfunction (hypothyroidism or hyperthyroidism)
  • Autoimmune hepatitis
  • Development of various autoantibodies 4

• Other serious complications:

  • Cardiovascular complications (arrhythmias, ischemic heart disease)
  • Renal lesions
  • Retinopathy
  • Hearing loss 4

Management of Side Effects

• Depression:

  • Screening and monitoring using depression rating scales
  • Early antidepressant intervention, particularly serotonin uptake inhibitors 7
  • For severe cases, interferon dose reduction or discontinuation may be necessary

• Flu-like symptoms:

  • Acetaminophen (up to 2 g/day) or NSAIDs
  • Dosing at night before bedtime 4

• Hematological side effects:

  • Regular monitoring of blood counts
  • Growth factors like erythropoietin for anemia and G-CSF for neutropenia may be considered, though evidence for routine use is limited 4, 6

Contraindications

Interferon therapy is contraindicated in patients with:

• Major, uncontrolled depressive illness
• Autoimmune hepatitis or conditions exacerbated by interferon
• Untreated hyperthyroidism
• Pregnancy or inability to comply with adequate contraception
• Severe concurrent diseases (severe hypertension, heart failure, significant coronary artery disease) 4

Clinical Pearls and Pitfalls

• Monitoring: Regular clinical examination, psychological assessment, blood counts, and thyroid function tests are essential during therapy 4

• Depression management: Healthcare providers, patients, and families should be informed about the risk of psychiatric disturbances with interferon therapy 7

• Thrombocytopenia: Low platelet counts may restrict initiation or maintenance of interferon-based therapies and increase risks during invasive procedures 6

• Pregnancy: Strict contraception is required during treatment and for 6 months afterward, particularly when interferon is combined with ribavirin 4

• Treatment duration: Varies based on the condition being treated and patient response, with hepatitis C typically requiring 24-48 weeks depending on viral genotype 4

Interferons remain important biological response modifiers with multiple clinical applications, but their use requires careful patient selection, monitoring, and management of side effects to optimize therapeutic outcomes.