B cells and antibodies Block A Flashcards
what does the adaptive immune response provide ?
specificity and diversity to make sure that the immune response is targeted to a specific and relevant microbe. It can respond to a large variety of microbes .
does the adaptive provide memory cells and why ?
It produces memory cells so that it has an increased ability to combat infection from the same microbe , this is how vaccines work
what allows the response to reset and why?
contraction and homeostasis so that there isn’t an excessive inflammation and bystander damage and also autoimmune disease.
what prevents an autoimmune disease ?
non reactivity to self antigens and commensal antigens
the B and T cells are key , what needs to occur and why with them ?
they need to be in contact by binding through receptors so that communication can occur
what are antibodies also called ?
immunoglobins , Ig
what are antibodies composed of ?
2 identical heavy chains , 2 identical light chains that re held together by disulfide bridges.
whats the 2 regions on an antibody ?
variable region - where binding to the antigen epitope occurs
constant region called the C terminus
what is the binding site of the antigen ?
epitope
does a single antigen have one or more epitopes ?
can have many
when are B cells generated ?
in the bone marrow
what do B cells express that recognise an antigen ?
BCR , B cell receptor
are all the BCR’s the same ?
no and this is what generated diversity to the adaptive immune response.
what makes the receptors on each lymphocyte differ ?
the recombination of gene segments
what’s BCR structure of the B cells ?
surface bound antibodies of the same specificity.
when does a b cell mature ?
when it expresses the functional BCR it matures from the bone marrow to enter the periphery where it migrates via the lymph nodes
stages of B cell activation ?
- Recognition of antigen by BCR leads to activation of B cell and internalisation of antigen
- Once internalised, antigen is broken down into peptides
- Peptides are loaded into MHC-II within the B cell and presented to antigen-specific CD4+ T cells – helper T cells
- If T cell also recognises antigen, provides ‘help’ to B cell (cytokines, costimulation)
- Allows B cell to fully activate into plasma cell and secrete antibodies.
what are C40L and CD40 ?
co stimulating factors for T cell
what occurs if a cell lacks the co stimulating factors ?
there is no cognate interaction between the B and T cell and there is no activation of the B cell so no antibodies are produced
what are Cd4+ ?
helper T cell surface proteins , MHC class II
how do CD4+ helper cells asisst ?
- Recognise the antigen
- Co stimulate
- Cytokine
what does the secretion of cytokines cause ?
- Induces proliferation of B cell and differentiation
- Plasma cell (antibody-secreting)
- Memory cell which are specific to antibody.
what’s the 3 functions of an antibody?
neutralisation
opsinisation
complement
neutralisation ?
a mechanism in which the antibody produced from the B cells will bind to the antigens on the viruses surface which results in it no longer being able to bind to the host cell and can therefore no longer take over the host cell to cause further damage. This is also done for viruses and their viral toxins.
opsinisation ?
involves the antibodies binding to the antigens on the viruses surface , however it does not block the viruses from binding to the host cell , instead it labels the pathogen so it Is recognised by a phagocytic cell so that the pathogen can be degraded using phagocytosis.
complement ?
the antibodies work together with the proteins involved in the complement system. When they bind together and bind onto a foreign cell this causes the membrane of the pathogen cell to swell up and burst
