1.1.3 Type IV Hypersensitivity Reactions Flashcards
How long do type IV hypersensitivity reactions take to develop?
24-72 hours of re-encounter
What cells are involved in type IV reactions?
Lymphocytes and macrophages
What triggers type IV reactions?
Environmental factors
Infectious microbes
Drugs
What are the different subtypes of type IV reactions?
Contact
Tuberculin
Granulomatous
What is granulomatous hypersensitivity?
Local immune response composed of macrophages and lymphocytes in response to foreign antigens that can not be removed/ destroyed from the host
What is the mechanism of tissue destruction in type IV reactions?
Sensitisation Phase
-APCs: macrophages present
-TH1 cells then activated
Effector Phase
-TH1 cells bind to resting macrophages
-Macrophage activation leads to immune response
How do type IV hypersensitivity reactions present?
Contact hypersensitivity
Granulomatous hypersensitivity
What occurs in contact hypersensitivity?
48-72 hours post exposure
Epidermal reaction, limited to zone of trigger
Requires endogenous proteins
What are the typical culprits of contact hypersensitivity?
Nickel
Poision Ivy
Latex
Organic chemicals
Nickel binds to host protein which then causes a response
How is contact hypersensitvity diagnosed?
Patch testing
When does granulomatous hypersensitivity occur?
21- 48 days post exposure
Causes tissue damage
Name 5 examples of granulomatous hypersensitivity
Tuberculosis
Leprosy (tuberculoid)
Schistosomiasis
Sarcoidosis
Tuberculin 48-72 hours, dermal reaction
What diseases are caused by endogenous antigens involved in type IV reactions?
Insulin-dependent diabetes mellitus
Antigen = pancreatic islet cells
Hashimoto’s thyroiditis
Hypothyroidism, antigen= thyroid gland
Hashimoto’s thyroiditis vs Graves’ disease
Hashimoto’s- low T3 and T4
B cells lead to necrosis/apoptosis of thyroid cells
CD8 T cells lead to apoptosis of thyroid cells
Thyroid cell death
Hypothyroidism
Grave’s- high T3 and T4
CD4 Tcells help B cells form TSH-B cell complexes
Increased TSH binding to TSH receptors and increased thyroid cell survival
Hyperthyroidism
Type III and IV hypersensitivity reaction therapuetic approaches
Anti-inflammatory and immunosupressive drugs:
-NSAIDs
-Corticosteroids (oral Prednisolone)
-Steroid sparing agents (reduce oral amount required)
Monoclonal antibodies:
-B cells
-Cytokines
