The symptoms of an immune complex reaction are due to which of the following?

• A. Activation of complement leading to inflammation
• B. Direct destruction of pathogens by cytotoxic T cells
• C. Release of histamine from mast cells without antigen-antibody interaction
• D. Production of antibodies against self-antigens

Answer: (A)

Verified step by step guidance

1. Understand that an immune complex reaction (Type III hypersensitivity) involves the formation of antigen-antibody complexes that deposit in tissues.
2. Recognize that these immune complexes activate the complement system, which is a part of the innate immune response.
3. Know that activation of complement leads to the generation of inflammatory mediators such as C3a and C5a, which attract neutrophils and cause inflammation.
4. Differentiate this from other immune responses: cytotoxic T cells (Type IV hypersensitivity) directly destroy infected cells, histamine release without antigen-antibody interaction is typical of anaphylaxis (Type I hypersensitivity), and production of antibodies against self-antigens is characteristic of autoimmune diseases.
5. Conclude that the symptoms of an immune complex reaction are primarily due to complement activation leading to inflammation.