Hypersensitivity Flashcards
(31 cards)
What 3 types of antigens can trigger hypersensitivity possibly leading to chronic diseases?
- Self-antigen
- Microbial antigen
- Environmental antigen
What is Type I Hypersensitivity also known as?
Immediate, IgE-mediated, allergy/atopy Hypersensitivity
Describe Type I Hypersensitivity
- Timing: within seconds to minutes
- Involves antigen-specific IgE on effector cells
- Vasoactive (Histamine) & eicosanoids and cytokines are released
*Most common type of hypersensitivity
Allergic rhinitis (hay fever), atopic asthma, anaphylaxis are examples of
Type I Hypersensitivity
Which types of Hypersensitivity are mediated by antibodies?
Type I, II, and III
Which type of hypersensitivity is local, tissue/cell specific?
Type II
Which type of hypersensitivity is general/systemic and related to immune complex deposition?
Type III
Which immunoglobulins have subtypes/subclasses?
IgA (2) & IgG (4)
Which immunoglobulin has the highest concentration and the longest half-life in the serum?
IgG
Which immunoglobulins have different forms?
IgA (monomer, dimer) & IgM (monomer, pentamer)
What is Type II Hypersensitivity also known as?
Antibody-mediated, cytotoxic
Describe Type II Hypersensitivity
- Timing: within minutes to hours
- Involves IgM and IgG
- 3 mechanisms
What is the complement and Fc receptor mediated mechanism of Type II Hypersensitivity?
Antibodies bind to antigens (allow direct binding of phagocytes on Fc portion) or activate complement (through classical pathway) which leads to inflammation (attract neutrophils).
Ex. Goodpasture Syndrome
Describe Goodpasture Syndrome
aka. anti-glomerular basement membrane disease
Antibodies are produced against basement membrane in kidney and lung.
Symptoms: bloody urine/lung, kidney failure
What is the opsonization and phagocytosis mechanism of Type II Hypersensitivity?
Antibodies opsonize the outside of cells and then phagocytes come and eat them up.
Ex. Idiopathic Thrombocytopenic Purpura (No platelets)
Ex. Autoimmune Hemolytic Anemia (AIHA)
Describe ITP
Auto-antibodies are produced against platelets. Platelets are opsonized and removed in the spleen.
Symptoms: easy/persistent nose bleeding
Describe AIHA
Auto-antibodies are produced against RBC membrane proteins.
Symptoms: faigue, jaundice, pallor (pale skin), weakness
What is the abnormal physiologic responses without cell/tissue injury mechanism of Type II Hypersensitivity?
- Graves’ Disease: Antibody binds TSH receptor (turns it on) without the presence of hormone/ligand. Causes hyperthyroidism.
- Myasthenia Gravis: Antibody binds ACh receptor and prevents ACh hormone from binding and signaling muscle contraction.
Acute rheumatic fever (myocardial antigens), pemphigus vulgaris (desmosomes), and pernicious anemia (intrinsic factors) are examples of
Type II Hypersensitivity
What is Type III Hypersensitivity also known as?
Immune Complex mediated
Describe Type III Hypersensitivity
- Timing: within hours
- Involves IgM and IgG
- Due to accumulations of immune complexes in vessels, joints causing complement/Fc receptor inflammation leading to attraction of neutrophils/macrophages (vasculitis).
Ex. Serum Sickness
Ex. Systemic Lupus Erythematosus (SLE)
What is an immune complex?
an antigen-antibody complex
What is serum sickness?
A phenomenon when patient makes antibodies against the foreign horse antibodies (against diphtheria) causing complex formation and deposition.
Describe SLE
SLE has type II hypersensitivity with blood (low WBC, RBC, and platelets), but majority of lupus symptoms are classic type III.
Symptoms: Malar rash (butterfly), fever, joint pain
