Immunity and the Immune System

Immunity

• Body parts involved: The immune system is comprised of various organs and tissues, including bone marrow, lymph nodes, spleen, and thymus.
• Function: The immune system protects the body from harmful pathogens, foreign substances, and abnormal cells. It identifies and eliminates these threats through a complex series of cellular and molecular events.
• Types: There are two main types of immunity: innate (natural) and adaptive (acquired).

Immune System: Front Line

• White blood cells (WBCs or leukocytes) are crucial components of the immune system.
• Granulocytes are a type of WBCs that includes neutrophils, eosinophils, and basophils.
• Agranulocytes are another type of WBCs that includes lymphocytes (B cells and T cells) and monocytes.

Immunity Terms

• Immunocompetent: The ability of the immune system to recognize and respond to antigens.
• Immunodeficiency: A state where the immune system is weakened and unable to adequately respond to challenges.
• Hypersensitivity: An exaggerated immune response to a normally harmless substance.
• Autoimmune disorders: Conditions where the immune system mistakenly attacks the body's own tissues.

Age-Related Changes in Immunity

• In older adults, the immune system undergoes several changes that make them more susceptible to infections and diseases.
• Inflammation: The inflammatory response, characterized by redness, swelling, heat, and pain, may be less effective in older adults due to decreased neutrophil activity.
• Antibody-Mediated Immunity: There may be a decline in the number and function of B lymphocytes, leading to reduced antibody responses.
• Cell-Mediated Immunity: There may be a decline in the number and function of T lymphocytes, impacting cell-mediated immunity.

Hypersensitivity

• There are four main types of hypersensitivities, each with its own mechanism and clinical manifestations.

Type I: Immediate/Rapid/Atopic

• Type I hypersensitivity is characterized by a rapid, IgE-mediated response that involves mast cell degranulation and release of histamine.
• This type of hypersensitivity underlies various allergic conditions such as anaphylaxis, allergic asthma, angioedema, and allergic rhinitis.
• Allergic Rhinitis: Common symptoms include sneezing, runny nose, itchy eyes, and congestion.
• Anaphylaxis: A life-threatening allergic reaction that involves the release of large amounts of histamine and other mediators, causing bronchospasm, hypotension, and cardiovascular collapse.
• Epinephrine Auto-Injector (EAI): A crucial device used to administer epinephrine in case of anaphylaxis. It is available in generic form and requires a prescription.

Type II: Cytotoxic

• Type II hypersensitivity involves antibody-mediated destruction of specific cells or tissues. Antibodies (IgG or IgM) target antigens on cell surfaces.
• Mechanism: The immune response may involve:
  • Antibody binding to cell surface receptors, altering their function.
  • Activation of the complement pathway.
  • Antibody-dependent cellular cytotoxicity (ADCC) where NK cells kill the target cell.
• Examples: Autoimmune hemolytic anemia, pernicious anemia, Graves disease, and Myasthenia Gravis.

Type III: Immune Complex-Mediated

• Type III hypersensitivity is triggered by the formation of immune complexes (antigen-antibody complexes) that deposit in tissues, activating complement and triggering inflammation.
• Mechanism: The immune complexes lodge in small vessels, leading to inflammation and tissue damage.
• Examples: Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

Type IV: Delayed

• Type IV hypersensitivity is a cell-mediated response, primarily involving T lymphocytes.
• This type of hypersensitivity does not involve antibodies or complement and typically takes more than 12 hours to develop.
• Mechanism: Delayed hypersensitivity reactions occur when antigens are presented to T-cells, leading to the activation of macrophages and the release of inflammatory mediators.
• Examples: Contact dermatitis (e.g., poison ivy), local reactions to insect stings, and positive tuberculin skin test (PPD).

Rheumatoid Arthritis (RA)

• Pathophysiology: RA is an autoimmune disorder where the immune system attacks the joints, leading to inflammation and damage.
• Mechanism: The autoimmune response leads to the production of rheumatoid factors (RF) and cytokines that contribute to joint destruction.
• Assessment:
  • Early Stage RA: Symptoms are generally mild and include fatigue, anorexia, morning joint stiffness, fever, weakness, and paresthesia.
  • Late Stage RA: Characterized by joint deformities (e.g., swan neck or boutonniere deformities), moderate to severe pain and morning stiffness lasting for hours.
  • Late Systemic Stage RA: May involve systemic complications like osteoporosis, severe fatigue, vasculitis, pericarditis, and renal dysfunction.
• Diagnosis: Requires a comprehensive evaluation by a rheumatologist, including medical history, physical examination, arthrocentesis (joint fluid analysis), laboratory tests like ESR, CRP, ANA, RF, and CCP antibodies, and imaging studies (X-rays, CT, or MRI).
• Pharmacology: Treatment involves a multi-faceted approach using:
  • NSAIDs (nonsteroidal anti-inflammatory drugs)
  • Steroids (corticosteroids)
  • Immunosuppressants (to suppress the immune response)
  • Disease-Modifying Antirheumatic Drugs (DMARDs)
    • Non-biologics: Methotrexate, sulfasalazine, hydroxychloroquine
    • Biologics: TNF inhibitors (e.g., etanercept), IL-6 inhibitors (e.g., tocilizumab)
  • Plasmapheresis (PLEX): A procedure that removes antibodies from the blood.
  • Surgical interventions: May be necessary to correct joint deformities or replace damaged joints.
• Treatment & Education:
  • Positioning: Maintaining proper posture and using supportive devices.
  • Heat/Cold Therapy: Applying heat or cold to joints for pain relief and inflammation management.
  • Low-Impact Exercise: Exercise is crucial to maintain mobility and strength, but should be low-impact to avoid stressing joints.
  • Self-Management and Promotion:
    • Body Image: Managing body image is crucial for people with RA.
    • Lifestyle Modifications: Eating a healthy diet, managing stress, and getting adequate rest can help improve overall well-being.

Systemic Lupus Erythematosus (SLE)

• Incidence/Prevalence: About 18,000 new cases of SLE are diagnosed annually. The condition is more prevalent in women, particularly during childbearing age.
• Pathophysiology: SLE is an autoimmune disorder where the immune system attacks the body's own tissues and organs.
• Mechanism: SLE involves the production of autoantibodies that target a variety of cellular components, leading to inflammation and damage.
• Types: SLE can present in various ways, with different symptoms and organ involvement.
• Assessment: Any tissue or organ can be affected in SLE.
• Diagnostic Findings:
  • Unexplained Fevers: Persistent low-grade fevers are a common feature.
  • Musculoskeletal: Joint pain, swelling, morning stiffness, fatigue, and muscle pain.
  • Dermatologic: Classic butterfly rash across the face, discoid rash (circular, raised, scaly patches), photosensitivity, alopecia, and oral ulcers.
  • Pulmonary: Pleuritis (inflammation of the lining of the lungs), pneumonitis (inflammation of the lungs).
  • Renal: Nephritis (inflammation of the kidneys), proteinuria (protein in the urine), and hematuria (blood in the urine).
  • Neurologic: Seizures, headaches, stroke, and cognitive dysfunction.
  • Hematologic: Anemia (low red blood cell count), thrombocytopenia (low platelet count), and leukopenia (low white blood cell count).
  • Cardiac: Pericarditis (inflammation of the sac surrounding the heart), myocarditis (inflammation of the heart muscle), and valvular abnormalities.
• Diagnosis: Requires a comprehensive evaluation by a physician, including physical examination, medical history, and laboratory tests.
• Laboratory Analysis:
  • Autoantibody Tests: A positive ANA (antinuclear antibody) test is a strong indicator of SLE.
  • Inflammatory Markers: Elevated ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) levels.
  • Creatinine Levels: To assess kidney function.
  • WBC Count: To assess the number of white blood cells, as SLE can cause leukopenia.
• Treatment:
  • AVOID the 4 S’s: Sun, Smoking, Stress, and Stressors.
  • Symptom Management: Medications, lifestyle changes, and supportive care aimed at relieving symptoms and improving quality of life.
  • Pharmacological Interventions:
    • Immunosuppressants:
      • Hydroxychloroquine: A medication used to treat lupus and other autoimmune conditions.
      • DMARDs (Disease-Modifying Antirheumatic Drugs): Medications that help slow down the progression of lupus and reduce inflammation.
      • Biologics: Medications that target specific immune system components to reduce inflammation.
    • Others: Anti-inflammatory drugs, anti-malarials, corticosteroids, and medications to manage specific organ complications.

Rash

• A rash is a delayed hypersensitivity reaction.

Histamine

• Histamine is a vasodilator.

Allergic Rhinitis

• Flunisolide (Flonase) can be used daily for allergic rhinitis.

Lupus and Rheumatoid Arthritis

• Think of lupus and rheumatoid arthritis (RA) when something is "free" in the blood.
• Lupus and RA are autoimmune diseases.

Early Signs of Rheumatoid Arthritis

• Fatigue
• Anorexia
• Morning joint stiffness
• Fever
• Weakness
• Paresthesia (numbness or tingling)

Late Signs of Rheumatoid Arthritis

• Joint deformities (swan neck, boutonniere)
• Moderate-to-severe pain
• Morning stiffness that lasts for hours

Rheumatoid Arthritis Lab Tests

• Erythrocyte sedimentation rate (ESR)
• C-reactive protein (CRP)
• Antinuclear antibody (ANA)
• Rheumatoid factor (RF)
• Cyclic citrullinated peptide (CCP) antibodies

Hydroxychloroquine

• Causes decreased energy and fatigue.
• Causes retinol damage, so annual eye exams are necessary.
• Safe during pregnancy.

Methotrexate

• Not safe during pregnancy.
• Avoid alcohol consumption.

Vaccines

• Differentiate between live and non-live vaccines.

Pain Relief

• Moving reduces pain in rheumatoid arthritis.
• Immobility can worsen pain.

Red, Hot Joint

• A single red and hot joint may indicate an infection.
• Report this finding to a medical professional.

Knee Elevation

• Avoid elevating the knees at night.
• Flexion of the knees can cause contractures and increase pain and stiffness in the morning.

Lupus

• Butterfly rash is a symptom of lupus.
• A diagnosis of lupus requires the presence of four signs and symptoms and positive laboratory tests.
• The three cardinal signs of lupus are butterfly rash, swollen joints, and unexplained intermittent fever.
• Lupus can affect multiple systems, including organs and skin.
• An antinuclear antibody (ANA) test is used to help diagnose lupus.
• People with lupus often have low white blood cell (WBC) counts.
• Pregnancy can worsen lupus.
• Avoid sun exposure, smoking, stress, and sepsis.

This quiz explores the essential components and functions of the immune system, including the types of immunity, the role of white blood cells, and key terminology. Test your knowledge on how the body protects itself from pathogens and maintains health.