Immune System Pathology Flashcards
Pathologies of the Immune System
- Hypersensitivity reactions
- Autoimmune disorders
- Immunodeficiencies
Hypersensitivity Disorders
- Hypersensitivity: disproportionate reactivity to an antigen.
- Hypersensitivity reaction: Immune responses to harmless antigens that cause symptoms upon re-exposure.
- Hypersensitivity disease: persistent and recurrent reaction to harmless antigen.
Type I Hypersensitivity - Steps
Immediate hypersensitivity. Reaction to common allergens.
Two step reaction:
1. Sensitization: IgE antibodies bind to mast cells
2. Subsequent exposure: Allergen binds to mast cell → degranulation → release of histamine → bronchospasm, vasodilation and increased permeability.
Causes localized and systemic anaphylaxis.
Type I Hypersensitivity - Symptoms
• Allergic rhinitis: most common, 10-30% of the population Symptoms: - Runny or stuffy nose - Sneezing - Red, itchy, and watery eyes - Swelling around the eyes
Anaphylaxis - Description and Cause
Life-threatening emergency, immediate epinephrine injection.
Exposure to large quantity of allergen.
Wide spread release of histamine → Increase vasodilation + airways constriction (drop in blood pressure).
Cause: Insect bites, stings. Food ingestion. Medication.
Type I Hypersensitivity - Treatment
- Anti-histamines: counteract histamine effects
- Corticosteroids: reduce inflammation (standard treatment)
- Epinephrine: induce vasoconstriction (prevent anaphylactic shock)
Type II Hypersensitivity - Description and Process
Cytotoxic hypersensitivity: antibody mediated destruction of healthy cells. Slightly delayed response (2-24h).
IgG antibodies recognize specific antigen and bind to a host cell:
a) Phagocytosis
b) Activation of compliment system (neutrophils, lytic death
c) Cellular dysfunction
Myasthenia Gravis (Type II) - Process
Antibody directed against nicotinic receptor.
Nerve impulse of motor neuron fail to pass the neuromuscular junction and stimulate contraction.
Myasthenia Gravis (Type II) - Symptoms
Slow progressive disease with fluctuations in symptoms.
- Double vision and dropping eyelid
- Fatigue while chewing
- Open jaw
- Difficulty swallowing
- Trouble talking & walking
Myasthenic crisis: Life-threatening, weakening resp. muscles
Type III Hypersensitivity - Process
Immune complex - mediated reaction: compliment activation and inflammatory reaction. Hours or days.
Antigen-antibody complexes deposit on basal lamina of blood vessels → Activation of compliment → Inflammation → Neutrophil degranulation and tissue damage.
Result: Vasculitis (skin, kidneys, joints, pleura, pericardium).
Systemic Lupus Erythematosus (Type III) - Symptoms
Antibodies against DNA and nuclear proteins.
- Rashes of the skin (UV exposure)
- Myalgia
- Polyarthritis
- Inflammation in the heart, lungs and kidneys
Type IV Hypersensitivity
T-cell mediated hypersensitivity. 24-72 hours from exposure.
CD8+ (cytotoxic) mediated: directly kills target cells. e.g. Type I diabetes.
CD4+ (t helper) mediated: T helper cells activate macrophage → secrete pro-inflammatory cytokines that damage tissues.
e.g. Multiple sclerosis.
Multiple Sclerosis - Description and Symptoms
Inflammatory disorder in CNS that compromises integrity of blood brain barrier. Irreversible axon loss and cell death that causes brain atrophy.
- Fatigue
- Pain
- Weakness & balance problems
- Sensory loss
- Visual dysfunction
- Spasticity and spasms
- Depression
Autoimmune Disease - Description and Treatment
Loss of tolerance towards self-antigens.
Treatment: corticosteroids & NSAIDs
Physical therapy if the disease impacts bones,
joints, or muscles.
Primary Immunodeficiency
Congenital conditions. Mutation to genes affecting the functioning of immune cells.
Secondary Immunodeficiency
Acquired. Various factors reduce the effectiveness of the immune response in an intrinsically normal immune system.
What can immunodeficiency lead to?
- Frequent and unusual (bad) complications of common infections (e.g. pneumonia)
- Opportunistic infections
- Increase prevalence of tumors.
Corticosteroids
Commonly prescribed to decrease inflammation.
Reduced production of pro-inflammatory cytokines and even lymphocytes in high dosage.
Can cause immunosuppression after prolonged usage.
HIV - Transmission and Description
Unprotected sexual intercourse and sharing needles.
HIV is a retrovirus: its genome is integrated in the DNA of CD4 T-cells → Infected T cells will produce new HIV viruses.
HIV - Progression
- Acute infection
- Latent period: asymptomatic HIV disease
- Early symptomatic HIV disease
- Advanced HIV disease or AIDS
HIV - Clinical Manifestation in Acute Infection
- Initially high viral load
- Production of antibodies (3-6 weeks)
- Reduction of circulating virus
Symptoms: - flu-like symptoms
- lymphadenopathy
HIV - Clinical Manifestation Latent Period
- No clinical symptoms
- Positive antibody test for HIV
- Without treatment it can last anywhere between 1 to 20 years.
HIV - Clinical Manifestation Early Symptomatic HIV Disease
- Persistent generalized lymphadenopathy
- Oral lesions
- Reactivation of shingles
- Hematological disturbances
HIV - Clinical Manifestation Advanced HIV Disease (AIDS)
- Neurological manifestation
- Weight loss
- Opportunistic infections
- Malignancies
- Fatigue
- Dermatological conditions
HIV - Treatment and Prognosis
Highly active antiviral therapy (HAART)
Manageable chronic illness for patients having access to
treatment and adhere to treatment.
