Hypersensitivities and autoimmunity are critical topics in NSG5140 (commonly a nursing or healthcare course focused on pathophysiology or advanced concepts in immunology).Hypersensitivity reactions are exaggerated or inappropriate immune responses that can lead to tissue damage. These reactions are classified into four types, with autoimmunity being a specific form of hypersensitivity where the immune system mistakenly targets the body’s own tissues.

Hypersensitivity reactions are exaggerated or inappropriate immune responses to antigens, leading to tissue damage or disease.

Types of Hypersensitivity Reactions

One

• • Involves IgE-mediated responses to soluble antigens.
  • Commonly associated with allergic reactions, such as hay fever and anaphylaxis.
  • Not typically involved in autoimmune disorders.

Two

• • Characterized by antibody-mediated destruction of target cells.
  • Autoantibodies bind to cell surface antigens, leading to complement activation and tissue injury.
  • Examples include autoimmune hemolytic anemia and Graves’ disease, where antibodies mimic hormones and cause overactivity of target organs.

Three

• • Involves the formation of immune complexes that deposit in tissues, leading to inflammation and damage.
  • Conditions like systemic lupus erythematosus (SLE) exemplify this type, where autoantibodies target nuclear components, resulting in widespread organ damage.

Four

• • A delayed-type response mediated by T cells rather than antibodies.
  • Conditions such as contact dermatitis and type 1 diabetes fall under this category, where T cells attack self-antigens

Autoimmunity

Autoimmunity occurs when the immune system fails to distinguish between self and non-self antigens, leading to sustained immune responses against the body’s own tissues. The mechanisms underlying autoimmunity include:

• Genetic Factors: Certain MHC (Major Histocompatibility Complex) genotypes are associated with increased susceptibility to autoimmune diseases due to their role in antigen presentation.
• Environmental Triggers: Factors such as infections, toxins, and dietary components can precipitate autoimmune responses in genetically predisposed individuals

Examples of Autoimmune Diseases

• Systemic Lupus Erythematosus (SLE): Characterized by a wide array of symptoms affecting multiple organ systems due to the presence of autoantibodies against nuclear antigens
• Graves’ Disease: An autoimmune disorder where antibodies stimulate the thyroid gland, leading to hyperthyroidism and associated symptoms like weight loss and rapid heartbea.
• Myasthenia Gravis: Involves autoantibodies targeting acetylcholine receptors at neuromuscular junctions, causing muscle weakness. ATP