Antibodies and case summary Flashcards
what is the structure of an antibody?
- The Fc part is CONSTANTmeaning that you can attach various things to this constant part without affectingthe binding ability of the antibody to the antigen
- The antigen binding part (Fab) is variable
how are magnetic beads used for?
Magnetic beads-‐this is a good way of pulling out a particular cell type from a sample of cells oE.g. if you want to purify T cells, you would have an antibody against CD3 and have it covalently attached to magnetic beads oThere are special columns you can buy which you put into a magnet and pass your sample through it so any cell thatis bound to a bead will be retained in the column •Therapeutically you can also add drugs to the antibodies -‐this can be used to target particular tumours for example
How do you generate monoclonal antibodies?
- You take a normal B lymphocytewhich is producing the antibody of interestand you FUSE IT with a myeloma cell line(which isn’t producing its own antibody)
- This gives you a HYBRIDOMA
- These cells have the ability to produce the antibody of interest
- Furthermore, as it is fused with a tumour cell, it can divide indefinitely
How to produce antibodies using recombinant DNA technology?
•You make a library of all the possible V segments•You display these V segments on a coat protein or bacteriophageso each bacteriophage is displaying different specificity V segments •Then you use this library of phages to screen plates that have the antigen mobilised on it •The phage with the correct specificity V segment will stick to the plate and the others can be washed off
How can you help patients who cannot produce antibodies and in what situations may this occur?
- If people can’t make their own antibodies then you can provide antibodies by giving IVIg
- Anti-‐cancer therapy-‐there are loads of therapies based on monoclonal antibodies targeting molecules that are over-‐expressed on certain types of tumours
- Removal of T cells from bone marrow grafts-‐this is important because the T cells cause graft-‐versus-‐host diseasein transplant
- So by removing the T cells with anti-‐CD3 antibody we can make sure that graft-‐versus-‐host disease doesn’t occur
Describe the different features depending on the ratio of antigen to antibodies?
- Ratio of antigen to antibodygoverns the size of the immune complex
- If you have a slight excessof antigen over antibodies then you tend to have smaller immune complexesthan when you have a lot of antibody and a small amount of antigen
- LARGERimmune complexes are recognised by the immune system and cleared more easily
- Smaller immune complexes don’t efficiently activate complement, it will only activate complement when it is bound to a surface (i.e. when it is deposited somewhere in the body)
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How do the different sized complexes affect further pathways?
- Large immune complexes will activate platelets and neutrophils
- Neutrophils will release mediators that affect the endothelial layer
- Smaller immune complexes will eventually pass through the cell layer and basement membrane and get trapped in the subendothelial layer
- Once they are stuck to a surface, theywill activate complement
- Following complement activation, neutrophils will be attracted to the small immune complexes
- This will lead to the cell membrane and basement membrane becoming damaged which will eventually lead to a detrimental effect on kidneyfunction
Describe the diffuse smear in a normal person?
n the serum of a healthy person, the diffuse smear at the top is the gamma globulin region
describe the diffuse smear in person who is developing active immunity?
you will get a lot more gamma globulinso the smudge will be darker.
•In this case the smear is also showing a polyclonal expansion•If you see a very sharp, single band, then this indicates amonoclonal expansion of B cells (e.g. myeloma)•If you did a bone marrow aspiration you will see some abnormal looking B cells and plasma cells in the bone marrow
