Fragment antigen-binding

Source: Wikipedia, the free encyclopedia.
(Redirected from
Fab region
)
Structure of a Fab with light and heavy chains.

The fragment antigen-binding region (Fab region) 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. The variable domain contains the paratope (the antigen-binding site), comprising a set of complementarity-determining regions, at the amino terminal end of the monomer. Each arm of the Y thus binds an epitope on the antigen.

Preparation

In an experimental setting,

immunoglobulin monomer into two Fab fragments and an Fc fragment. Conversely, the enzyme pepsin cleaves below the hinge region, so the result instead is a F(ab')2 fragment and a pFc' fragment. 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]

  • Heavy and light chains, variable and constant regions of an antibody.
    Heavy and light chains, variable and constant regions of an antibody.
  • An antibody digested by papain yields three fragments: two Fab fragments and one Fc fragment
    An antibody digested by papain yields three fragments: two Fab fragments and one Fc fragment
  • An antibody digested by pepsin yields two fragments: a F(ab')2 fragment and a pFc' fragment
    An antibody digested by pepsin yields two fragments: a F(ab')2 fragment and a pFc' fragment

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.[2]

Applications

Theraputics

Fabs have seen some therapeutic use in

Fc region is removed.[5]

Fabs are a common form-factor for

TNFα
.

Diagnostics

Fab antibodies also have diagnostic use.

Sulesomab, an antigen that recognizes proteins on the surface of granulocytes, is used to label out infections, again using the 99mTc isotope.[7]

Fab fragments are often fused to small proteins (<100 kDa) that have lower scattering, resulting in images with less contrast.

See also

References

  1. ISBN 0-8493-6078-1
    .
  2. ISBN 0-8153-3642-X
    .
  3. S2CID 40869324
    .
  4. S2CID 44916236.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  5. PMC 2992890
    .
  6. ^ Fachinformation Lucentis. Novartis Pharma. Stand 15. November 2007.
  7. ^ W. J. Köstler, C. C. Zielinski (November 2000). "Diagnostische und therapeutische Antikörper in der Onkologie — State of the Art". Acta Chirurgica Austriaca. 32 (6): 260–263.


Stub icon

This immunology article is a stub. You can help Wikipedia by expanding it.

Retrieved from "https://en.wikipedia.org/w/index.php?title=Fragment_antigen-binding&oldid=1200261504"