In: Anatomy and Physiology
Although both type I and type II hypersensitivities involve antibodies as immune effectors, different mechanisms are involved with these different hypersensitivities. Differentiate the two.
Differentiation between type 1 and type 2 hypersensitivity.
Firstly we learn what is hypersensitivity: Hypersensitivity or allergy occur when we are sensitized to an antigen, again comes in contact with same antigen .
This results in following reactions ,eventhough both type 1 and type 2 involves antibodies , their mechanism is different and the type of antibodies involved is different and they are differentiated below
Type -1 hypersensitivity reactions | Type -2 hypersensitivity reactions |
1. A type 1 hypersensitivity is an immediate hypersensitivity reaction and is also called anaphylaxis | 1.Type.- 2 hypersensitivity reaction is called cytotoxic hypersensitivity |
2.This is mediated by IgE antibodies | 2.This is mediated by IgG and IgM antibodies. |
3.Mechanism : when we are exposed to an antigen , (allergen ) , antigen-specific IgE antibodies bind to and activates mast cells and basophills .which release their granular contents by degranulation . Deep explaination: IgE antibodies bind via their Fc receptors to mast cells ,when an antigen bind to it cross linking take place and results in degranulation. |
3.Mechanism : when an antibody reacts with antigen on cell surface ,the cell is marked for destruction by number of ways ,this is usual procedure ,but in type 2 the antibodies are directed aganist self-antigen . Deep explaination: IgG or IgM binds to cellular antigen and results in complement fixation and cell lysis. |
4.This results in release of mediators like histamine which constricts smooth muscle ,cause vasodilation and increase vascular permeability |
4.The above action results in destruction of body's own tissues (auto immune disease) |
5.Examples include local and systemic anaphylaxis . There is profound bronchoconstriction and shock due to extensive vasodilation . | 5.Haemolytic diseases of new born and blood transfusion reactions are examples of type 2 hypersensitivity |