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Antibody isotopes
HND Immunology
Question | Answer |
---|---|
Name the immunoglobulin classes. | IgG, IgA, IgM, IgD, IgE. |
Describe immunoglobulin G. | Produced in response to protein antigens, it makes up 80% of the total antibodies in serum. It has a molecular weight of 150kD with 4 sub-types; IgG1, IgG2, IgG3 and IgG4. Provides the bulk of immunity to blood born infections. |
What response does IgG play a major part in? | Secondary response. |
What is special about IgG? | It is the only antibody that can cross the placenta. |
Describe immunoglobulin A. | A 170kD monomer in serum that exists as a 340kD dimer in external secretions. Dimer contains secretory component and a separate joining chain, it is found in colostrum, milk and saliva and provides immunity at mucosal surfaces and against micro-organisms. |
Describe immunoglobulin M. | The first antibody to be produced during primary response, it is expressed on the surface of B cells as a monomer and acts as the B cell receptor. As a free antibody in the blood it exists as a pentamer with a molecular weight of 900kD. |
Describe immunoglobulin D. | Found at low levels in serum, this monomer acts as an antigen binding site on B cells as it is also expressed on the B cell surface. |
Describe immunoglobulin E. | Only present at low levels in serum. Has a role in inflammation and allergy but gives protection against parasites. Binds to mast cells via it's Fc region and causes their de-granulation. |
What is released from mast cells during their de-granulation ? | Histamines. Cytokines. Granulocyte macrophage colony-stimulating factor (GM-CSF), heparin and proteases. |
What is the second form of IgA and where can it be found? | Secretory IgA, can be found in tears, saliva, sweat and breast-milk. |
How many hyper-variable domains are found on IgG? | 12 as IgG is a monomer and has 3 hyper-variable domains each for its two heavy chains and two light chains. |
How many hyper-variable domains are found on IgA? | Internal monomeric from has 12 hyper-variable domains like IgG, but dimeric form has 24 hyper-variable domains. |
How many hyper-variable domains are found on IGM? | IgM is a pentamer as a free antibody in blood, with each sub-unit containing 12 hyper-variable domains, meaning it has 60 hyper-variable domains overall, IgM expressed on B cell surfaces are monomers and so have 12 hyper-variable domains. |
How many hyper-variable domains are found on IgD? | IgD is a monomer with 12 hyper-variable domains. |
How many hyper-variable domains are found on IgE? | IgE is a monomer with 12 hyper-variable domains. |
What assortment can there be in the type of light chains present on an antibody? | Kappa-kappa or lambda-lambda, can not be kappa-lambda. |
What type of bond stabilises the 3D structure of an antibody? | Disulphide bonds. |
How do the heavy chains of an antibody compare to each other? | They are identical. |