11.4 Immune System Disorders
4 min read•august 28, 2024
The immune system, our body's defense mechanism, can sometimes malfunction, leading to various disorders. These include immunodeficiencies, autoimmune diseases, and allergies. Each affects the body differently, from weakening our defenses to attacking our own tissues.
Understanding these disorders is crucial for grasping how the lymphatic and immune systems work together. Whether it's the overreaction in allergies or the self-attack in autoimmune diseases, these conditions highlight the delicate balance our immune system must maintain for optimal health.
Immune System Disorders
Categorization and Immunodeficiencies
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Top images from around the web for Categorization and Immunodeficiencies
Diseases and Disorders of the Immune System | Boundless Anatomy and Physiology View original
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Frontiers | Are All Primary Immunodeficiency Disorders Inborn Errors of Immunity? View original
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Approach to Primary Immunodeficiencies for the Non-Immunologist Physicians View original
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- Immune system disorders can be broadly categorized into immunodeficiencies, autoimmune diseases, and hypersensitivity reactions (allergies)
- Immunodeficiencies are conditions where the immune system is compromised or weakened, leading to increased susceptibility to infections
- They can be primary (genetic) or secondary (acquired)
- Primary immunodeficiencies are inherited disorders caused by genetic mutations that affect the development or function of immune cells
- Examples include severe combined immunodeficiency (SCID) and X-linked agammaglobulinemia (XLA)
- Secondary immunodeficiencies are acquired conditions resulting from factors that suppress the immune system
- Causes include malnutrition, certain medications (chemotherapy), or infections (HIV/AIDS)
Autoimmune Diseases
- Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues, causing inflammation and damage
- The immune system fails to distinguish between self and non-self antigens
- Examples of autoimmune diseases include rheumatoid arthritis, systemic lupus erythematosus (SLE), multiple sclerosis, type 1 diabetes, and Hashimoto's thyroiditis
Allergic Reactions
Causes and Mechanisms
- Allergic reactions are hypersensitivity responses of the immune system to typically harmless substances called allergens
- Common allergens include pollen, dust mites, animal dander, and certain foods
- Allergies involve an exaggerated response by the immune system, particularly the production of IgE antibodies specific to the allergen
- Upon initial exposure to an allergen, the immune system becomes sensitized, and IgE antibodies are produced and attach to mast cells and basophils
- Subsequent exposure to the same allergen triggers the release of histamine and other inflammatory mediators from mast cells and basophils, leading to the symptoms of an allergic reaction
Symptoms and Anaphylaxis
- Symptoms of allergic reactions can range from mild to severe
- May include itching, redness, swelling, hives, runny nose, watery eyes, sneezing, coughing, and difficulty breathing
- Anaphylaxis is a severe, potentially life-threatening allergic reaction
- Can cause rapid onset of symptoms such as difficulty breathing, throat swelling, and a drop in blood pressure
- Requires immediate medical attention and the use of epinephrine (adrenaline) to counteract the effects
Autoimmune Disorders
Rheumatoid Arthritis (RA)
- Rheumatoid arthritis (RA) is an autoimmune disorder that primarily affects the joints, causing inflammation, pain, stiffness, and eventual joint damage
- The immune system attacks the synovial membrane lining the joints
- Treatment for RA includes:
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Disease-modifying antirheumatic drugs (DMARDs) such as methotrexate
- Biological agents that target specific components of the immune system (TNF inhibitors)
- Physical therapy and occupational therapy can help improve joint function and manage daily activities
Systemic Lupus Erythematosus (SLE or Lupus)
- Systemic lupus erythematosus (SLE or lupus) is a chronic autoimmune disorder that can affect multiple organ systems
- Commonly affects the skin, joints, kidneys, blood cells, brain, heart, and lungs
- Lupus is characterized by the production of autoantibodies that form immune complexes and deposit in tissues, causing inflammation and damage
- Treatment for lupus depends on the severity and organ involvement
- May include NSAIDs, antimalarial drugs (hydroxychloroquine), corticosteroids, immunosuppressants (cyclophosphamide), and targeted biological therapies (belimumab)
- Patients with lupus require regular monitoring for disease activity, organ damage, and potential complications
Immune System in Transplantation and Cancer
Transplant Rejection
- Transplant rejection occurs when the recipient's immune system recognizes the transplanted organ or tissue as foreign and mounts an immune response against it
- Major histocompatibility complex (MHC) molecules, also known as human leukocyte antigens (HLAs), play a crucial role in transplant rejection
- Mismatches in HLAs between the donor and recipient increase the risk of rejection
- Types of transplant rejection include:
- Hyperacute (immediate)
- Acute (within days to weeks)
- Chronic (months to years after transplantation)
- Immunosuppressive drugs are used to prevent and treat transplant rejection by suppressing the immune response
- Examples include calcineurin inhibitors (cyclosporine, tacrolimus), antimetabolites (mycophenolate mofetil), and corticosteroids
Cancer Immunology and Immunotherapy
- The immune system plays a complex role in cancer development and progression
- The immune system can recognize and eliminate cancer cells (immunosurveillance)
- Cancer cells can also evade immune detection and suppress immune responses (immunoediting)
- Cancer immunotherapy aims to harness the immune system to fight cancer
- Approaches include immune checkpoint inhibitors (anti-CTLA-4, anti-PD-1/PD-L1), adoptive cell therapy (CAR T-cell therapy), and cancer vaccines
- The success of cancer immunotherapy depends on factors such as:
- Immunogenicity of the tumor
- Presence of tumor-infiltrating lymphocytes
- Immunosuppressive tumor microenvironment