Immune System Disorders chapter 13

Immune Disorders

Disorders associated with the immune system:
- Immunodeficiencies: Lack of a properly functioning immune system.
- Autoimmunity: Immune responses directed toward “self”.
- Hypersensitivities: Excessive or inappropriately directed immune responses.

Primary Immunodeficiencies:
- Present from birth.
- Genetic in nature.
- Rare.
- Deficiencies in humoral, cellular, and/or innate responses.
Secondary Immunodeficiencies (acquired):
- Infections (AIDS, hepatitis, EBV, measles).
- Chronic illnesses (diabetes, some cancers).
- Medications & Treatments (cancer chemotherapy & radiation therapy, immunosuppressive drugs).
- Environmental or lifestyle factors (malnutrition, alcoholism).
- Aging.

Failure of self-tolerance leads to immune responses against tissues, causing chronic conditions.
Multi-factorial causes and risk factors:
- Genetic pre-disposition.
- Exposure to certain infectious agents.
- Sex (women have a higher rate of some).
- Environmental Factors (Vitamin D deficiency).
Diagnosis is often difficult due to generalized symptoms and varied disorders.
Detection of autoantibodies may suggest an autoimmune disease.
Managing autoimmune disorders:
- Immunosuppressive drugs.
- Replacement (insulin for Type 1 Diabetes).
- Monoclonal Antibodies (biologics, generic drug name often ends in “mab”).

Inappropriate, exaggerated immune response to harmless antigens.
Classified into 4 categories:
- 3 are antibody-based (humoral).
- 1 is T-cell based (cellular).

Commonly called “allergies”.
Involves overproduction of IgE antibodies against harmless substances (allergens).
Excessive histamine production by mast cells and basophils.
Onset is immediate upon exposure.
Sensitization: Prior exposure to the allergen is required.
Systemic anaphylaxis:
- System-wide allergic reaction, can be rapidly fatal.
- Treatment: Epinephrine, Benadryl.
- Medical emergency.
Diagnosis: Challenge tests identify specific triggers.
Management:
- Over-the-counter medications.
- Desensitization immunotherapy (trigger IgG production).
Increasing due to genetic component, industrialized countries, hygiene hypothesis.
Intolerances: Lactose, gluten.

“Cytotoxic” reactions.
IgG binding to cell surfaces triggers complement system or NK cells for destruction.
Examples: myasthenia gravis, Graves disease.
ABO Blood Transfusion Reactions:
- Antibodies against blood types you don’t have.
- Transfusion reaction if wrong type is given, often fatal.
Hemolytic Disease of the Newborn:
- Rh incompatibility between mother and fetus.
- Preventable: Rh- mothers treated with Rhogam.

Immune Complex (soluble antigens + IgM/IgG antibodies).
Complexes block capillaries and deposit into tissues, triggering complement and inflammation.
Serum sickness: complication of artificial passive immunization.
Examples of Autoimmune Type III Hypersensitivities: Systemic Lupus Erythematosus, Rheumatoid Arthritis, Scleroderma.