Understanding Hypersensitivity Type 3

Understanding Hypersensitivity type 3, also known as immune complex mediated hypersensitivity, arises when the body’s attempt to fight off infection or foreign substances backfires. This occurs when immune complexes, formed by antibodies binding to antigens (foreign molecules), accumulate in various tissues.  These complexes trigger an inflammatory response, damaging tissues and leading to a range of symptoms.

Understanding Hypersensitivity Type 3

Causes of Hypersensitivity Type 3:

  • Infections: Bacterial, viral, or parasitic infections can trigger the formation of immune complexes that deposit in tissues, leading to reactions.
  • Autoimmune Diseases: In certain autoimmune diseases like lupus, the immune system mistakenly attacks the body’s own tissues, leading to the formation of immune complexes that contribute to tissue damage.
  • Serum Sickness: This reaction can occur after receiving injections of foreign serum (blood products from another animal species) used in some treatments. The body forms immune complexes against the foreign proteins in the serum, leading to symptoms.

The Formation and Attack in Hypersensitivity Type 3:

  • Antigen Encounter: The immune system encounters an antigen (foreign molecule) from an infection, medication, or in autoimmune diseases, body tissues.
  • Antibody Production: Antibodies are produced to target and neutralize the antigen.
  • Immune Complex Formation: In some cases, the ratio of antibodies to antigens is not ideal, leading to the formation of immune complexes – clusters of antibodies bound to antigens.
  • Complement Activation: These immune complexes can activate the complement system, a group of proteins that further promotes inflammation.
  • Tissue Damage and Inflammation: Immune complexes deposit in various tissues, triggering an inflammatory response that damages surrounding cells.

Symptoms of Hypersensitivity Type 3:

Symptoms vary depending on the location of immune complex deposition. Here are some common examples:

  • Skin: Serum sickness can cause urticaria (hives), vasculitis (inflammation of blood vessels), and itching.
  • Joints: Arthritis with joint pain, swelling, and redness can occur.
  • Kidneys: Glomerulonephritis (inflammation of the kidney filters) can lead to blood or protein in the urine, high blood pressure, and kidney failure in severe cases.
  • Lungs: Alveolitis (inflammation of the air sacs in the lungs) can cause cough, shortness of breath, and chest pain.

Diagnosis and Management of Hypersensitivity Type 3:

  • Blood Tests: Blood tests can help identify signs of inflammation and potential autoimmune diseases.
  • Imaging Tests: X-rays or ultrasounds may be used to visualize joint damage or assess kidney function.
  • Biopsy: In some cases, a tissue sample (biopsy) may be needed to confirm the diagnosis.
  • Identifying and Avoiding Triggers: In cases like serum sickness, avoiding the triggering serum is crucial. Identifying and treating underlying infections can also help.
  • Medications: Anti-inflammatory medications like corticosteroids can help manage symptoms and reduce inflammation.
  • Immunosuppressive Medications: In severe cases, medications that suppress the immune system may be used to control the immune response.

Conclusion:

Understanding Hypersensitivity type 3 can be a challenging condition due to its varied presentations. However, by understanding the causes, symptoms, and treatment options, individuals can work with healthcare professionals to manage the condition and improve their quality of life.

https://en.wikipedia.org/wiki/Type_III_hypersensitivity

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