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Phl p 2: Difference between revisions

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<StructureSection load='2vxq' size='350' side='right' scene='' caption='Pollen allergen Phl p 2 (grey) complex with antibody heavy chain (red) and light chain (aqua) (PDB code [[2vxq]]) '>
{{STRUCTURE_3kle|  PDB=3kle  | SIZE=400| SCENE= |right|CAPTION=HIV-1 reverse transcriptase complex with DNA and AZTPPPPA, [[3kle]] }}


==Immune system==
==Immune system==
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Antibodies are made up of 2 pairs of light and heavy chains. The heavy chains of antibodies are specific to each isotope with: α, δ, ε, γ, and μ corresponding to: IgA, IgD, IgE, IgG, and IgM respectively. The light chain of the antibody is separated into two categories for mammals: lambda (λ) and kappa (κ). Antibodies are further differentiated into two regions: the constant region and the variable region. Like their names suggest, the constant region stays the same for its specific isotope however the variable region changes to accommodate many different antigens. The two ends of the variable region contain sites called Fabs which stands for fragment antigen binding region. This region is the area where the beta sheets of the antibody bind specifically to antigens. The constant region of the antibody is made up of 2 heavy chains specific to each isotope. This region is also called the Fc region or the fragment, crystallizable region. This end of the antibody mediates the next step of immune response for the given isotype which in turn allows for different types of responses.
Antibodies are made up of 2 pairs of light and heavy chains. The heavy chains of antibodies are specific to each isotope with: α, δ, ε, γ, and μ corresponding to: IgA, IgD, IgE, IgG, and IgM respectively. The light chain of the antibody is separated into two categories for mammals: lambda (λ) and kappa (κ). Antibodies are further differentiated into two regions: the constant region and the variable region. Like their names suggest, the constant region stays the same for its specific isotope however the variable region changes to accommodate many different antigens. The two ends of the variable region contain sites called Fabs which stands for fragment antigen binding region. This region is the area where the beta sheets of the antibody bind specifically to antigens. The constant region of the antibody is made up of 2 heavy chains specific to each isotope. This region is also called the Fc region or the fragment, crystallizable region. This end of the antibody mediates the next step of immune response for the given isotype which in turn allows for different types of responses.
[[Image:Antibody_basic_structure.gif]]
[[Image:Antibody_basic_structure.gif|left|thumb|450px]]


==Type I Hypersensitivity==
==Type I Hypersensitivity==
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==Phl p 2 and huMab2==
==Phl p 2 and huMab2==
Publication Abstract from PubMed


We report the three-dimensional structure of the complex between the major respiratory grass pollen allergen Phl p 2 and its
{{ABSTRACT_PUBMED_19201867}}
specific human IgE-derived Fab. The Phl p 2-specific human IgE Fab has been isolated from a combinatorial library constructed
from lymphocytes of a pollen allergic patient. When the variable domains of the IgE Fab were grafted onto human IgG1, the
resulting Ab (huMab2) inhibited strongly the binding of allergic patients’ IgE to Phl p 2 as well as allergen-induced basophil
degranulation. Analysis of the binding of the allergen to the Ab by surface plasmon resonance yielded a very low dissociation
constant (KD � 1.1 � 10�10 M), which is similar to that between IgE and Fc�RI. The structure of the Phl p 2/IgE Fab complex
was determined by x-ray crystallography to 1.9 Å resolution revealing a conformational epitope (876 Å2) comprised of the planar
surface of the four-stranded anti-parallel �-sheet of Phl p 2. The IgE-defined dominant epitope is discontinuous and formed by
21 residues located mostly within the � strands. Of the 21 residues, 9 interact directly with 5 of the 6 CDRs (L1, L3, H1, H2, H3)
of the IgE Fab predominantly by hydrogen bonding and van der Waals interactions. Our results indicate that IgE Abs recognize
conformational epitopes with high affinity and provide a structural basis for the highly efficient effector cell activation by allergen/IgE immune complexes. ''High-Affinity IgE Recognition of a Conformational Epitope of the Major Respiratory Allergen Phl p 2 As Revealed by X-Ray Crystallography'' by Sivaraman Padavattan,2* Sabine Flicker,2† Tilman Schirmer,* Christoph Madritsch,†
Stefanie Randow,‡ Gerald Reese,‡ Stefan Vieths,‡ Christian Lupinek,† Christof Ebner,§
Rudolf Valenta,3,4†¶ and Zora Markovic-Housley3*The Journal of Immunology, 2009, 182: 2141–2151.


[[Image:Phlp2_huMab2_direct_contacts.jpg]]
[[Image:Phlp2_huMab2_direct_contacts.jpg]]


In this experiment it was determined that IgE antibodies bound to <scene name='Phl_p_2/Phl_p_2/2'>Phl p 2</scene>, a grass pollen allergen, in allergic patients rather than IgG antibodies. This was strange because both antibodies are capable of specifically binding Phl p 2 however IgE antibodies are the least abundant in mammalian immune systems whereas IgG antibodies are one of the most abundant. Researchers predicted that the epitope specific heavy chain of the IgE antibody bound to a different epitope on the pollen than did the IgG antibody and that the IgE epitope had a much higher affinity for the antigen than the IgG antibody. To test this hypothesis, researchers took the constant region of an IgG antibody (Fc receptor) and paired it when the variable region of the allergen specific IgE epitope (Fab region). Researchers then termed this new antibody huMab2 which had the IgE Fab region and the IgG Fc region. The huMab2 antibody had a new <scene name='Phl_p_2/Heavy_chain/1'>heavy chain</scene> and a new  
In this experiment it was determined that IgE antibodies bound to <scene name='Phl_p_2/Phl_p_2/5'>Phl p 2</scene>, a grass pollen allergen, in allergic patients rather than IgG antibodies.<ref>PMID:19201867</ref> This was strange because both antibodies are capable of specifically binding Phl p 2 however IgE antibodies are the least abundant in mammalian immune systems whereas IgG antibodies are one of the most abundant. Researchers predicted that the epitope specific heavy chain of the IgE antibody bound to a different epitope on the pollen than did the IgG antibody and that the IgE epitope had a much higher affinity for the antigen than the IgG antibody. To test this hypothesis, researchers took the constant region of an IgG antibody (Fc receptor) and paired it when the variable region of the allergen specific IgE epitope (Fab region). Researchers then termed this new antibody huMab2 which had the IgE Fab region and the IgG Fc region. The huMab2 antibody had a new <scene name='Phl_p_2/Heavy_chain/3'>heavy chain</scene> and a new <scene name='Phl_p_2/Light_chain/2'>light chain</scene>. It was important for researchers to keep the Fc region of the IgG antibody because the Fc region does not bind mast cells to cause degranulation and allergic reaction when exposed to Phlp2 antigen.  
<scene name='Phl_p_2/Light_chain/1'>light chain</scene>. It was important for researchers to keep the Fc region of the IgG antibody because the Fc region does not bind mast cells to cause degranulation and allergic reaction when exposed to Phlp2 antigen.  


When huMab2 was mixed in solution with mast cell bound IgE antibodies it actually prevented the binding of Phl p 2 with IgE as the IgG like antibody was more abundant and free floating in solution. This was a significant discovery because this research information can be used and applied to further develop the treatment of type I hypersensitivity patients.
When huMab2 was mixed in solution with mast cell bound IgE antibodies it actually prevented the binding of Phl p 2 with IgE as the IgG like antibody was more abundant and free floating in solution. This was a significant discovery because this research information can be used and applied to further develop the treatment of type I hypersensitivity patients.
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There was a large interface between the antigen and antibody where 21 allergen residues were involved, and 25 Fab residues were involved.
There was a large interface between the antigen and antibody where 21 allergen residues were involved, and 25 Fab residues were involved.
The antibody recognized a four-stranded beta sheet with the residues glu30, glu32, asp34, and his36 on beta 3, ala43 on beta 4, asn65, arg67, phe68, and met74 on beta 6, met74, lys75, asn76, val77, and phe78 on beta 7, and asp39, glu40, trp41, gly73, asp74, asp80, and pro94 in the loops near the c-term on <scene name='Phl_p_2/Allergen_interface_residues/1'>phl p 2</scene>.
The antibody recognized a four-stranded beta sheet with the residues glu30, glu32, asp34, and his36 on beta 3, ala43 on beta 4, asn65, arg67, phe68, and met74 on beta 6, met74, lys75, asn76, val77, and phe78 on beta 7, and asp39, glu40, trp41, gly73, asp74, asp80, and pro94 in the loops near the c-term on <scene name='Phl_p_2/Allergen_interface_residues/1'>phl p 2</scene>.
*<scene name='Phl_p_2/Cpk_colored/2'>All interactions</scene>.
*<scene name='Phl_p_2/Spacefilled_residues/1'>Spacefilled interface residues</scene>


<scene name='Phl_p_2/Cpk_colored/2'>all interactions</scene>.
<scene name='Phl_p_2/Spacefilled_residues/1'>spacefilled interface residues</scene>


==Reference==
==Reference==
Sivaraman Padavattan,2* Sabine Flicker,2† Tilman Schirmer,* Christoph Madritsch,†Stefanie Randow,‡ Gerald Reese,‡ Stefan Vieths,‡ Christian Lupinek,† Christof Ebner,§Rudolf Valenta,3,4†¶ and Zora Markovic-Housley3*. High-Affinity IgE Recognition of a Conformational Epitope of the Major Respiratory Allergen Phl p 2 As Revealed by X-Ray Crystallography.The Journal of Immunology, 2009, 182: 2141–2151.
<references/>

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