Third Line of Defence - Introduction + B-Cell Response & Antibodies Flashcards
State characteristics of Third Line of Defence
4 characteristics
- is slow to activate compared to 2nd line of defence
- provides immunological memory
- is specific to particular pathogen
- involves B and T cell responses
Explain 1st stage in B-Cell Response
Antigen presenting phagocytes
Macrophages and Dendritic cells engulf pathogen, break it down and present fragement on their MHC-2. This fragment acts as a foreign antigen
Explain 2nd stage in B-Cell Response
T-helper cell
A unique T-helper cell binds to the foreign antigen using the complementary T-cell receptor. The Th-helper cell is now activated. It detaches and searches for the B-cell.
How are T-helper cells unique?
The T-cell receptor is randomly generated in hopes of it being complementary to pathogenic protein
Explain 3rd stage in B-Cell Response
B-Cell
At the same time as 1st and 2nd stage, a unique B-cell with a complementary B-cell receptor binds to the same type of pathogenic antigen. It takes it in, breaks it down and presents it on its MHC-2. The T-helper cell eventually binds to it and causes B-cell to divide rapidly.
Explain 4th stage in B-cell Response
Plasma cells
The B-cells divides to produce plasma cells which release specific antibodies capable of binding to the pathogenic antigen.
Explain 5th stage in B-cell response
Memory cells
B-cell also divides to produce memory B-cells, which live for a long time (possibly whole life). When they bind to same pathogenic antigen in the future, the divide very fast to produce lots of plasma cells which in turn produces lots of specific antibodies again. Pathogen destroyed before symptoms arise.
What are antibodies and tehir characteristic?
They are ‘Y’ shaped proteins produced by plasma cells in 3rd line of Defence that are specific to a particular antigen
Describe structure of antibodies
Heavy chains that make up Y shape, light chains that sit beside arms of the heavy chains. Variabel region at both ends of the Y arms
What is the variable region
Describe structure of antibodies
Heavy chains that make up Y shape, light chains that sit beside arms of the heavy chains. Variabel region at both ends of the Y arms
Just go c notes cus I cant put pics in here ugh
What is the variable region?
Region is the antibody binding site
What are the two things antibodies can do?
- Aggulation
- Neutralisation
Explain Aggulation
Since antibodies have 2 variable regions they can stick pathogens together. This stops the pathogens from being able to cause disease by damaging cells. Eventually they are engulfed by phagocytes.
Explain Neutralisation
Bacteria releases toxins which can damage our cells. Toxin molecules act as antigens and can be stuck together by antibodies. Toxic substaces are said to be neutralised when stuck together and are eventually engulfed.
