Type II Hypersensitivity Flashcards
What is type II hypersensitivity also known as?
Antibody-mediated cytotoxic hypersensitivity.
What is type II hypersensitivity?
Type II hypersensitivity is an antibody-mediated process in which IgG and IgM antibodies are directed against antigens on cells.
What are some examples of type II hypersensitivity?
Delayed haemolytic transfusion reaction.
Haemolytic disease of the newborn.
Immune thrombocytopenia.
Graves’ disease hormones.
What is immune thrombocytopenia?
Where antibodies develop against platelet surface proteins
What is Graves’ Disease?
Where patients develop thyroid stimulating antibodies that bind the thyrotropin receptor resulting in secretion of thyroid hormones.
What can type II hypersensitivity reactions be a result of?
Exposure to a foreign antigen (e.g. some drugs that bind to the surface of cells, blood transfusions, or organ transplants) or the incorrect response to a self-antigen resulting in antibodies that recognise cell surface structures.
What types of antibodies are responsible for T2 hypersensitivity reactions?
IgGs and IgMs.
What are the three mechanisms in which the antibodies produced can cause disease?
Anti-receptor activity blocks or activates its function.
Antibody-dependent cell-mediated cytotoxicity (ADCC).
Classical activation of the complement cascade (something binds to antibody causing a huge shitstorm that results in inflammation, opsonization and lysis).
What happens in the classical pathway when antibodies on the surface of cells are recognized by the complement components?
Formation of the membrane attack complex (MAC) in the surface of the cell, leading the cell death due to loss of osmotic integrity (cell swells until it bursts as it can no longer regulate what comes in and out).
Also results in inflammation, opsonisation (antibodies clump antigens together) and recruitment/activation of other immune cells.
What is ADCC?
Antibody-antigen complexes on the surface of cells are bound by Fc receptors which bind the constant, not antigen-specific, tail regions of IgM and IgG antibodies. NK cells lead to directed lysis of the target cell, but also the release of inflammatory mediators, chemokines and cytokines.
What is an example of a type of cell that expresses the Fc receptor?
Granulocytes.
Type II hypersensitivity can result in multiple mechanisms of tissue injury including…?
Local or systemic inflammation, cell depletion leading to a loss of function or imbalance in organ function.
