Changes

[[Image:LH Ig.png|thumb|200px|right|'''Immunoglobulin''' <br> Asher Allison 2008]]

[[Image:LH Ig.png|thumb|200px|right|'''Immunoglobulin''' <br> Asher Allison 2008]]

* Antibody consists of two identical heavy (H) chains and two identical light (L) chains

Antibodies are "Y-shaped" and consist of two identical heavy (H) chains and two identical light (L) chains with each H chain being linked to an L chain. The heavy chain consists of 4 or 5 protein domains, 1 amino terminal variable domain and 3 or 4 constant domains. Each light chain has one variable and one constant domain. Each arm of the molecule consists of one L chain and part of an H chain and there are two identical antigen-binding sites on each antibody molecule, one at the tip of each arm. The binding sites are made up of a combination of the variable domains of 1H and 1L, although single cells only have receptors of one specificity.  The antigen binding site of an antibody is determined by a combination of the amino acid sequence of both the heavy and light chain variable domains (VH and VL). Antibodies of different specificities have different amino acids within one of three regions of the variable domains and these are called the hypervariable regions. The '''variable domains''' are '''folded''' in such a way as to form a pocket into which antigens fit. The '''constant domains''' do '''not''' bind antigen, although they determine the biological functions of the antibody molecules.

** Each H chain is linked to an L chain

* The heavy chain consists of 4 or 5 protein domains

** 1 amino terminal variable domain and 3 or 4 constant domains

At the carboxyl terminus of B-cell expressed Ig is a region that holds the antibody molecule in the cell membrane. Secreted 'free' antibodies do not possess this region. The '''Fab''' fragments of the immunoglobulin is the '''antigen binding fragment''' generated from the light chains when digested by papain (proteolytic enzyme). The  '''Fc''' fragment is the fragment produced by '''papain from the heavy chains''' and this fragment '''mediates phagocytosis''', triggers '''inflammation''' and '''targets Ig''' to certain tissues.

* Each light chain has one variable and one constant domain

** Each arm of the molecule consists of one L chain and part of an H chain

** There are two identical antigen-binding sites on each antibody molecule

*** One at the tip of each arm

*** Made up of a combination of the variable domains of 1H and 1L

* Single cells only have receptors of one specificity

* The antigen binding site of antibody is determined by a combination of the amino acid sequence of both the heavy and light chain variable domains (VH and VL)

** Antibodies of different specificities have different amino acids within one of three regions of the variable domains

*** These are called the hypervariable regions

** The '''variable domains''' are '''folded''' in such a way as to form a pocket into which antigens fit

* The '''constant domains''' do '''not''' bind antigen

** They determine the biological functions of the antibody molecules

* At the carboxyl terminus of B-cell expressed Ig is a region that holds the antibody molecule in the cell membrane

** Secreted antibodies do not possess this region

*The '''Fab''' fragments of the immunoglobulin is the '''antigen binding fragment''' generated from the light chains when digested by papain (proteolytic enzyme)

*The  '''Fc''' fragment is the fragment produced by '''papain from the heavy chains'''

**The Fc fragment '''mediates phagocytosis''', triggers '''inflammation''' and '''targets Ig''' to certain tissues.

==Function==

==Function==