Questions and Answers
What does BCR stand for?
B cell receptor
What are the 5 classes of antibodies?
IgG, IgM, IgA, IgE, IgD
Which antibodies have a hinge region?
Antibodies can have only one antigen binding site.
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What are the two main types of chains in an antibody?
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The carbohydrate structure on an antibody helps in ____.
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What is the Fab region of an antibody?
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Which enzyme can cut above the hinge region?
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What is the primary function of hypervariable regions (HV) in antibodies?
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Match the following antibody classes with their symbols:
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Study Notes
Structure of Antibodies and BCR
- B Cell Receptor (BCR) is an antibody functioning as a receptor on B cells.
- T Cell Receptor (TCR) is found on T cells and does not secrete antibodies.
Serum Antibodies
- Activated B cells, known as plasma cells, produce serum antibodies.
- Antibodies, also referred to as immunoglobulins (Ig), are glycoproteins essential for immune functions.
- There are 5 main classes (isotypes) of antibodies:
- IgG (Gamma) - 5 constant regions
- IgM (Mu) - 5 constant regions
- IgA (Alpha) - 4 constant regions
- IgE (Epsilon) - 4 constant regions
- IgD (Delta) - 4 constant regions
- Each class has subisotypes, denoted as Ig1, Ig2, etc.
Antibody Structure
- Antibodies have a Y-shaped structure consisting of two arms, with 4 total polypeptide chains: 2 light chains and 2 heavy chains.
- Chains are held together by disulfide bonds.
- Each antibody features:
- A hinge region that provides flexibility in binding.
- Antigen binding sites specific to one epitope.
- IgG, IgA, and IgD contain a hinge region; IgM and IgE do not but can still exhibit flexibility.
Functional Structure
- Each antibody (monomer) has 2 antigen binding sites originating from the variable domains of heavy and light chains, referred to as the Fab region.
- Antibodies activate complement and bind to phagocytes through the constant region known as the Fc region; this interacts with Fc receptors on effector cells.
Proteases in Antibody Study
- Proteases are used to explore antibody structures and in immune diagnostics.
- Two key proteases:
- Papain: Cleaves antibodies into 2 Fab and 1 Fc fragments.
- Pepsin: Cuts below the hinge region, producing F(ab)2 fragments (can bind antigens but lack biological activity).
Genetic Engineering and Domain Structure
- Single chain antibodies feature only the variable region, known as Fv (fragment variable).
- Antibodies share a conserved structure, including amino acid sequences and a beta barrel or beta sandwich arrangement attributed to the immunoglobulin (Ig) domain.
- Disulfide bonds between beta strands contribute to the stability of the structure.
Hypervariable Regions
- Most variability in immunoglobulins resides in the variable regions, specifically the three hypervariable regions (HV1, HV2, HV3).
- The specificities of antibodies result from differences in these hypervariable regions among various antibodies.
Complementarity Determining Regions (CDR)
- Each arm of an antibody contains three complementarity determining regions (CDRs), formed by the combination of hypervariable regions from both light and heavy chains.
- CDRs play a crucial role in determining the specificity of antibody-antigen interactions.
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Description
This quiz explores the structure and function of antibodies, including their classification and the role of B cell receptors (BCR). Understand the different isotypes of immunoglobulins and their importance in the immune system.
