8. Hypersensitivity Flashcards
What is the other name for:
Type I Hypersensitivity?
What is the general mediator?
Immediate Hypersensitivity
Mediators are secreted by Mast Cells (eg. Histamine)
What is the other name for:
Type II Hypersensitivity
What are the general mediators?
Antibody Mediated
Antibodies that bind tissue antigens and cause compliment dependent tissue injury.
What is the other name for:
Type III Hypersensitivity?
What are the general mediators?
Immune complex mediated hypersensitivity
Abs bind circulating antigens and form immune complexes, which deposit in vessels and cause classical complement-dependent injury.
What is the other name for:
Type IV Hypersensitivity?
What are the general mediators?
T Cell Mediated Hypersensitivity
Mediated by T Cells and result from Th1 / Th17 cytokines or CD8+ T Cells killing host cells.
What is the function of the following in Type I Hypersensitivity?
Histamine
Dilation of small blood vessels and increased vascular permiability
Smooth muscle contraction
What is the function of the following in Type I Hypersensitivity?
Proteases
May cause local tissue damage
What is the function of the following in Type I Hypersensitivity?
Prostaglandins
Vasodilation
What is the function of the following in Type I Hypersensitivity?
Leukotrienes
Smooth muscle contraction
What is the function of the following in Type I Hypersensitivity?
Cytokines
Induction of inflammation, and the late-phase reaction
What happens upon initial exposure to an allergen?
B Cells begin making IgE as a response to Th2 cells reacting to the antigen, and then those IgE antibodies are picked up by mast cells’ FcRε.
What important cell in allergy contains an FcRε receptor?
Mast Cells
How long does the late phase reaction of type I hypersensitivity take to occur?
2 to 24 hours
What three cell types are found in large quantities in areas undergoing a late phase reaction?
Neutrophils, eosinophils, T Cells
What type of hypersensitivity is responsible for Grave’s Disease and Myasthenia Gravis?
Type II hypersensitivity. Antibodies for self cell receptors cause overactive or inhibited cell functions.
What causes injury in Type III Hypersensitivity?
Complement and Fc receptor mediated inflammation
What is the primary cause of tissue injury in Type IV hypersensitivity?
Th1 and Th17 cells releasing cytokines to stimulate inflammation and activate macrophages
CTLs killing host cells
What type of hypersensitivity is responsible for Systemic Lupus Erythematosus, Chron’s Disease, and Multiple Sclerosis?
Type III
What causes the tissue damage associated with Type IV hypersensitivity?
Products of the recruited macrophages and neutrophils
NO,
Lysosomal Enzymes,
ROS,
Proinflammatory cytokines
What sort of hypersensitivity reaction would be responsible for a positive PPD / TB test?
Type IV / Delayed type hypersensitivity reaction
What type of hypersensitivity is responsible for Allergic Contact Dermatitis (ACD)?
Type IV
What is the most common source of sensitization to chromium?
Leather
What leads to the formation of granulomas?
Prolonged exposure to cytokines, which activate macrophages, cause the generation of Th1 cells, and recruit leukocytes.
What are the “principal clinical manifestations” of Systemic Lupus Erythematosus according to slide 33?
Rashes
Arthritis
Glomerulonephritis
What are the most frequent auto antibodies found in Systemic Lupus Erythematosus?
Anti-DNA antibodies
What is the principal diagnostic test for Systemic Lupus Erythematosus?
Anti-nuclear antibodies
What type of hypersensitivity is responsible for Rheumatoid Arthritis?
Type II / Type III
(Mixed)
What all cells would be involved in Rheumatiod Arthritis?
Th1, Th17, Macrophages, B Cells, Plasma Cells
(Easy to remember because RA is both Type II and Type III)
What is the cause of Rheumatoid Arthritis?
Circulating IgM and IgG specific for self Fc regions of non-immune IgG causes inflammation and cartilage / bone destruction in the synovium.
Vasoactive amines (like histamine) can dilate certain vessles and constrict others. How is this possible?
They are vasodilators for capillaries that don’t have smooth muscle around. They are vasoconstrictors for post-capillary venules that do have smooth muscle around, because they contract smooth muscle.
What type of hypersensitivity is responsible for Multiple Sclerosis?
Type IV
What is the basic pathogenesis of Multiple Sclerosis?
Microglia present antigens to T Cells, which leads to an excess of Glutamate somehow. Oligodendrocytes are sensitive to Glutamate, so they die, causing demyelination of the nerves.
Also the damaging TNF-α and O2 / NO can damage nerves
What type of hypersensitivity is responsible for Type 1 Diabetes Mellitus?
Type IV
What type of hypersensitivity is responsible for Inflammatory Bowel Disease?
Type IV
What is the basic pathogenesis of Inflammatory Bowel Disease?
Host immune response to commensal flora
