Type III Hypersensitivity

Definition

Type III hypersensitivity, also known as immune complex-mediated hypersensitivity, occurs when antibodies bind to soluble antigens, forming immune complexes that deposit in various tissues and trigger inflammatory responses. This immune response is primarily driven by IgG and IgM antibodies and can lead to tissue damage and a variety of clinical manifestations. The condition is often linked to autoimmune disorders and can be exacerbated by persistent infections or chronic exposure to certain antigens.

5 Must Know Facts For Your Next Test

1. Type III hypersensitivity reactions can lead to conditions such as serum sickness, systemic lupus erythematosus (SLE), and rheumatoid arthritis due to the accumulation of immune complexes in tissues.
2. The clinical manifestations of type III hypersensitivity include vasculitis, glomerulonephritis, and arthritis, depending on where the immune complexes deposit.
3. These reactions are characterized by delayed onset, often appearing hours to days after exposure to the antigen, which complicates diagnosis and management.
4. Treatment options may involve immunosuppressive therapy to reduce inflammation or corticosteroids to control symptoms associated with tissue damage from immune complexes.
5. A classic example of type III hypersensitivity is the reaction following the administration of antiserum or vaccines that contain horse serum, leading to serum sickness due to the formation of immune complexes.

Review Questions

• How do immune complexes form in type III hypersensitivity, and what role do they play in tissue damage?
  • Immune complexes form when antibodies bind to soluble antigens in the bloodstream, resulting in clusters of these complexes that can deposit in various tissues. When these deposits accumulate, they trigger an inflammatory response mediated by complement activation and recruitment of inflammatory cells. This inflammation can lead to tissue damage, manifesting as conditions like vasculitis or glomerulonephritis.
• Discuss how type III hypersensitivity is linked to autoimmune disorders and provide examples of diseases associated with this hypersensitivity reaction.
  • Type III hypersensitivity is closely associated with autoimmune disorders because these conditions often involve the formation of autoantibodies that bind to self-antigens, creating immune complexes. Examples include systemic lupus erythematosus (SLE), where immune complexes contribute to widespread organ damage, and rheumatoid arthritis, where they can lead to joint inflammation. These diseases highlight how dysregulation in the immune response can lead to significant pathology through type III mechanisms.
• Evaluate the impact of environmental factors on the development of type III hypersensitivity reactions in individuals with autoimmune predispositions.
  • Environmental factors such as infections, medications, and exposure to certain antigens can significantly influence the development of type III hypersensitivity reactions, especially in genetically predisposed individuals. For instance, infections may increase the production of specific antibodies that bind to antigens related to the infection or self-antigens, forming immune complexes. This can exacerbate existing autoimmune conditions or trigger new hypersensitivity responses. Understanding these interactions helps inform preventative strategies and therapeutic approaches for managing autoimmunity.

Related terms

Immune Complex: An immune complex is formed when an antibody binds to an antigen, leading to a cluster of molecules that can provoke an immune response and inflammation.

Complement System: The complement system is a part of the immune system consisting of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens, often activated during type III hypersensitivity.

Autoimmune Disorders: Autoimmune disorders occur when the immune system mistakenly attacks the body's own tissues, sometimes involving type III hypersensitivity reactions due to the formation of immune complexes.