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T-cell and B-cell interaction TB Notes.docx

3 Pages
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Department
Health Sciences
Course Code
HTHSCI 3I03
Professor
Jonathan Bramson

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B-cell activation  Occurs in spleen and lymph nodes  CD4+ Helper T-cell  T-cell help= causes somatic hypermutation (affinity maturation) and isotype switching  Going to get plasma cells or memory cells (i.e. maturation) following proliferation B-cell Antigens  Thymus dependent vs. thymus independent  Thymus dependent= T-cell help, MHCII required o Co-stimulation (“signal 2”)= coming from the T-cells o Protein antigens and maybe carbohydrates o Somatic hyper-mutation (more IgG produced because remember that the initial Ab produced is IgM), isotype switching o Involves conventional B2 cells  Thymus independent= no T-cell required (more innate activity) o Co-stimulation= but does not come from T-cell= TLRs Activated!! o Carbohydrates (i.e. polysaccharides) o Little somatic hypermutation and little isotype switching o Therefore= less IgG than with thymus dependent o B1 cells and marginal zone B-cells Three outcomes of B-cell activation  Neutralization (Antibodies bind to the outside)  Opsonization (i.e. extracellular bacteria)  Classical pathway of complement activation 1) T-cell binds to B-cell 2) Triggers CD40 ligand up-regulation 3) Then CD40L on T-cell 4) IL-4 synthesis increases in the T-cell 5) Interaction causes the rearrangement of the actin skeleton= directs IL-4 directly to that space to control the amount of activation *** Note: CD40L/CD40 interaction is IMPORTANT FOR B-CELL SURVIVAL!! Linked Recognition  B-cells can only be recognized by T-cells that recognize the same antigen  I.e. the epitope that the T-cell receptor recognizes should be bound by the B-cells  Steps o Virus particle recognized by Ab and internalized by your B-cell o Break down and present the viral proteins on MHC o T-cell recognizes protein and activates B-cell o B-cell is activated= can secrete Ab that are specific to the antigen o Can protect against autoimmunity Vaccine response  Used linked recognition to boost T-cells  Tag a tentanus taxoid protein (toxin of a bacteria that has been neutralized)—link to a polysaccharide  B-cell will internalize the polysaccharide  Will break down the particle  Will have protein and polysaccharide bound to MHCII  B-cell will present this  I.e. can easily vaccine against the taxoid protein  T-cell will come along and recognize the B-cell o Get B-cell response to the polysaccharide (i.e. encapsulated bacteria are now bound by Ab!!) T-cell and B-cell
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