Bradley Monk: Created page with "The fragment antigen-binding (Fab fragment) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy ..."

2013-07-03T22:43:11Z

Created page with "The fragment antigen-binding (Fab fragment) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy ..."

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The fragment antigen-binding ([[Fab]] fragment) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy and the light chain. These domains shape the paratope — the antigen-binding site — at the amino terminal end of the monomer. The two variable domains bind the epitope on their specific antigens.
[[File:Fab.png|thumb|300px]]
In an experimental setting, Fc and [[Fab]] fragments can be generated in the laboratory. The enzyme papain can be used to cleave an immunoglobulin monomer into two [[Fab]] fragments and an Fc fragment. The enzyme pepsin cleaves below hinge region, so a F(ab')2 fragment and a pFc' fragment is formed. Recently another enzyme for generation of F(ab')2 has been commercially available. The enzyme IdeS (Immunoglobulin degrading enzyme from Streptococcus pyogenes, trade name FabRICATOR) cleaves IgG in a sequence specific manner at neutral pH. The F(ab')2 fragment can be split into two [[Fab]]' fragments by mild reduction.[1]

The variable regions of the heavy and light chains can be fused together to form a single-chain variable fragment (scFv), which is only half the size of the [[Fab]] fragment, yet retains the original specificity of the parent immunoglobulin.

Fab Fragment - Revision history

Bradley Monk: Created page with "The fragment antigen-binding (Fab fragment) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy ..."