Immune System Diseases and Disorders

Chapter 5: Immune System Diseases and Disorders

Chapter Objectives

  • By the end of this chapter, you should be able to:

    • 5.1 Define the terminology common to the immune system and the disorders of the system.

    • 5.2 Discuss the basic anatomy and physiology of the immune system.

    • 5.3 Identify the important signs and symptoms associated with common immune system disorders.

    • 5.4 Describe the common diagnostics used to determine the type, cause, or both of an immune system disorder.

    • 5.5 Identify disorders of the immune system.

    • 5.6 Describe the typical course and management of common immune system disorders.

    • 5.7 Describe the effects of aging on the immune system and the common disorders of the system associated with aging.

Anatomy and Physiology of the Immune System

Key Organs

  • Thymus Gland: Plays a crucial role in developing T-cells (T lymphocytes).

  • Bone Marrow: Responsible for the production of blood cells, including immune cells.

  • Lymph Nodes: Filters lymph fluid and is essential for immune response.

  • Spleen: Filters blood, removes old blood cells, and helps fight infections.

  • Liver: Processes nutrients and detoxifies the blood; involved in immune responses.

  • Tonsils: Help protect against pathogens entering through the mouth or nose.

Immune Response

  • Specific Immune Response: Targeted action against particular pathogens involving antigen and antibody reactions.

  • Nonspecific Immune Response: General defensive mechanisms that include:

    • Inflammation: A localized response to tissue injury characterized by redness, warmth, swelling, and pain.

    • Phagocytosis: The process by which certain cells engulf and digest pathogens.

    • Physical Barriers: Skin and mucous membranes that prevent pathogen entry.

    • Chemical Barriers: Substances like acids and enzymes in secretions that deter pathogens.

  • First Line of Defense: Consists of physical and chemical barriers to prevent pathogen entry.

Types of Immunity

  • Active Natural Immunity: Acquired through infection and recovery, leading to memory of the pathogen.

  • Active Artificial Immunity: Developed through vaccination, where an antigen is introduced to stimulate immune response.

  • Passive Natural Immunity: Acquired through the transference of antibodies from mother to child, such as via breastfeeding.

  • Passive Artificial Immunity: Immunity gained through the administration of antibodies from another source (e.g., immunoglobulin treatment).

Common Signs and Symptoms of Immune Disorders

  • Signs and symptoms vary depending on the organ involved and the type of immune disorder, including:

    • Immunodeficient: A scenario where there is a lack of immunity leading to frequent infections.

    • Autoimmune: Conditions where the immune system attacks the body’s own tissues.

    • Isoimmune: Immune responses against tissues of other humans.

Diagnostic Testing for Immune Disorders

  • Common diagnostic tests include:

    • Skin Tests: Used to identify allergies.

    • Desensitization: A treatment strategy for allergies involving gradual exposure.

    • Blood Count: Evaluates levels of immune cells in the blood.

    • Coombs Test: Detects antibodies that act against red blood cells.

    • Antinuclear Antibody (ANA) Test: Identifies autoimmune disorders by detecting autoantibodies.

    • Rheumatoid Factor (RF) Test: Assesses for specific antibodies in rheumatoid arthritis.

Hypersensitivity Disorders

  • Allergies: A hypersensitivity reaction that can result in symptoms including:

    • Common Reactions: Urticaria (hives), contact dermatitis, etc.

    • Symptoms: Elevated eosinophil count, redness, heat, swelling, itching, runny nose, coughing, sneezing, wheezing, nasal congestion.

Specific Examples of Hypersensitivity Disorders

  • Hay Fever:

    • Reaction to allergens in the mucous membranes of the nose and upper respiratory tract.

    • Symptoms: Sneezing, watery eyes, runny nose, itching.

    • Causes: Seasonal (tree pollen, grasses) vs. nonseasonal (dust mites, pet dander).

  • Asthma (Bronchial Asthma):

    • Symptoms: Extreme shortness of breath, difficulty breathing, wheezing, anxiety, cough.

  • Anaphylaxis:

    • A severe, life-threatening allergic reaction with symptoms such as itching of the throat, tongue, and scalp; face and airway edema leading to difficulty breathing.

    • Treatment: Emergency tracheostomy, epinephrine, corticosteroids, antihistamines.

  • Food Allergies:

    • Can include reactions to various foods like chocolate or shellfish.

    • Common Symptoms: Cramping, diarrhea, vomiting.

  • Contact Dermatitis:

    • An acute or chronic allergic skin reaction caused by exposure to substances like cosmetics, laundry products, plants, jewelry, paint, or drugs.

Autoimmune Disorders

  • Rheumatoid Arthritis:

    • Characterized by abnormal antibodies that attack the body's own cells and tissues.

    • RF Antibody: Its presence in the blood is indicative of the disease.

    • Classic Sign: Ulnar deviation, frequently affecting fingers, wrists, elbows, feet, and knees.

  • Myasthenia Gravis:

    • Slow onset with symptoms including diplopia (double vision), ptosis (drooping eyelids), dysphagia (difficulty swallowing), dysphonia (difficulty speaking), inability to maintain facial expressions, and general fatigue.

  • Lupus Erythematosus:

    • Two types: cutaneous (limited to skin) and systemic (diffuse, affecting multiple systems).

  • Scleroderma:

    • Characterized by hardening, thickening, and shrinking of connective tissues, including skin.

    • Features periods of remission and exacerbation, joint contractures, and Raynaud’s phenomenon.

Isoimmune Disorders

  • Blood Transfusion Reaction:

    • Type O is the universal blood donor; Type AB is the universal blood recipient.

    • Symptoms of Reaction: Commonly include chills, shivering, and fever.

  • Erythroblastosis Fetalis:

    • Occurs when a mother's antibodies attack the antigen on the baby’s red blood cells, potentially leading to severe consequences.

    • Typically, no complications occur with the first Rh-positive baby born to an Rh-negative mother, but later pregnancies may result in complications.

Organ Rejection

  • This occurs when the human immune system attacks transplanted tissue. Factors influencing rejection include:

    • More closely matched donor decreases the chance of rejection.

    • Acute Rejection: Happens early post-transplant.

    • Chronic Rejection: Occurs over a long period and can lead to organ failure.

Immune Deficiency Disorders

  • Defined as the inability of the immune system to protect against diseases; can be congenital, genetic, or acquired. Acquired types may result from:

    • Bone marrow suppression from chemotherapy or radiation.

    • Medications taken by organ transplant recipients.

    • Acquired Immunodeficiency Syndrome (AIDS):

    • Caused by the Human Immunodeficiency Virus (HIV) which eradicates the individual’s lymphocytes. The virus is fragile and easily destroyed.

    • Transmission Routes:

      • Sexual intercourse.

      • Sharing of hypodermic needles.

      • In utero transmission from infected mother to unborn baby.

Rare Diseases

  • Severe Combined Immunodeficiency Disease (SCID):

    • Represents a group of inherited disorders leading to partial or complete dysfunction of the immune system.

Effects of Aging on the Immune System

  • The aging process can lead to:

    • Degeneration of the thymus gland, impacting the production of T-cells.

    • Altered function of antibodies, affecting immune responses.

    • General reduction in resistance to diseases, making older adults more susceptible to infections and immune disorders.

Knowledge Check Activities

  1. Knowledge Check Activity 5-1: A classic sign of rheumatoid arthritis is:

    • Options: hand pain, headaches, ulnar deviation, leg pain.

    • Answer: c. Ulnar deviation is a classic symptom of rheumatoid arthritis.

  2. Knowledge Check Activity 5-2: Which of the following is considered a hypersensitivity disorder?

    • Options: HIV, rheumatoid arthritis, lupus, hay fever.

    • Answer: d. Hay fever is a type of hypersensitivity disorder.

Self-Assessment

  • Imagine your friend was just diagnosed with rheumatoid arthritis. Describe the testing that someone may go through to determine if they have rheumatoid arthritis.

Summary

  • The chapter provided an exhaustive overview of the immune system, its disorders, diagnostics, treatments, and the impact of aging on immune function.