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Immunological Response

A response by the immune system is launched in response to the recognition of an antigen. An antigen is any sort of protein, enzyme, or ligand that is not from self. By self, we refer to the body to which the immune system belongs.

-For example, my immune cells will not attack self-cells. AKA cells that belong to my own body


There are many different kinds of immunoglobulin’s and they carry out different functions. Some act during an allergic response and other cuts and scrapes. They are composed of heavy chains and light chains which have a constant and variable region. The variable region allows for recognition of different antigens. They function in a few different ways:

1.Activation of Complement Pathway
4.Killing by Oxidation
6.Antibody-Dependent Cellular Cytotoxicity

The way immunoglobulin’s interact with antigens in the following methods

1.Hydrogen Bonding
2.Ionic Bonding
3.Hydrophobic interactions
4.Van-der Waals Forces

IgG- Most abundant immunoglobulin; Can cross placental membrane; Functions in Complement Pathway-Classical

IgM- Membrane bound pentamer on B cells; Due to large size, its found predominantly in blood

IgA-Secretory immunoglobulin; Found in digestive track as well as breast milk, mucus, and tears; Second most common in humans

IgE-Involved in hypersensitivity/allergic reactions

IgD- Serves as a B cell receptor

Complement Pathway

This is a series of cascade reactions that involves the use of complement proteins found in serum. These proteins are secreted by macrophages, liver cells, and epithelial cells. The major take away form this is that we want to form the Membrane Attack Complex. The MAC basically form a hole in the membrane of a cell allowing for nutrients and water to flow freely which leads to cell death.

Main Functions

-Enhanced phagocytosis
-Lysis of microorganism
-inflammatory mediator

1) Classical Pathway

- This is an antibody dependent mechanism.
- Antigen will be bound by immunoglobulin
-This will cause a series of reactions and break down of compliment proteins.
-Eventually this will make MAC that will lead to cell death.

2) Alternative Pathway

- This is an antibody independent mechanism.
-Activated by recognition of foreign cell surface (i.e. bacterial cell wall)
-This will also cause a series of reactions with complement proteins
-Eventually this will also lead to formation of MAC