HS IV Flashcards
What type of reaction is a type IV hypersensitivity reaction?
Delayed reaction, due to involvement of lymphocytes and macrophages
How long does it take for a type IV hypersensitivity reaction to occur?
1-3 days
What immune cells are involved in type IV hypersensitivity reactions and how do they cause tissue damage?
Lymphocytes and macrophages
- Macrophages antigen present, activating naive T cells to become memory and antigen specific TH1 cells
- Activated T cells release cytokines which attract macrophages and cause tissue damage
Define contact hypersensitivity
Epidermal reaction causing eczematous rash in response to exogenous antigen
What is a tuberculin hypersensitivity?
A dermal reaction producing swelling and induration (hardened mass)
What is a granulomatous hypersensitivity?
Persistence of antigens causing tissue damage, involves walling off infected cells by forming a granuloma of T cells containing macrophages
What causes a granulomatous hypersensitivity and how long does it take to develop?
Infection with TB, leprosy or schistosomiasis, or sarcoidosis
How does the Mantoux/Lepromin test work?
- Antigen injected into the subcutaneous tissue
- TH1 effector cell recognises antigen and releases cytokines
- Recruitment of phagocytes to injection site
- Visible red bump indicates sensitisation
Describe the pathophysiology of Hashimoto’s disease
Presence of CD8+ T cells and autoantibodies against thyroid cells
Release of cytokines and activation of macrophages damages thyroid tissue, causing hypothyroidism
Describe the features of hypothyroidism
Weight gain Fatigue Myalga/Arthralga Decreased appetite Cold intolerance
What antibodies are tested for in Hashimoto’s disease?
Anti-thyroglobulin antibody
Anti-thyroid peroxidase antibody
Describe the likely results of a biopsy of a thyroid gland with Hashimoto’s disease
Infiltrate of lymphocytes (CD4+ and CD8+)
Plasma cells
How is Hashimoto’s disease tested?
Replacement therapy with thyroxine
Monitor TSH levels
What cells are damaged in insulin dependant diabetes mellitus?
Pancreatic islet cells
