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• Thema 1 Hoorcolleges

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• How does the B cell recognize an antigen, and a T cell?

  B cell recognizes an antigen by the antibody. This antibody can be on the membrane (= B cell receptor) or free form (antibody). 
  
  T cell receptor binds the antigen when it is bound to a MHC molecule

• How is the development of T cells?

  Precursors in the bone marrow. they go to the thymus, there they get their education. THey generate their repetoire and go int he circulation and different lymph node most of those T cells will never react to the antigen they are mode for.
  
  progenitor cels - proliferation - double-negtive  Tcells commit to T lineage
  rearrangement bèta genes - checkpoint for pre-TCR
  proliferation double negative pre-T cell
  rearrangement alfa genes - checkpoint for TCR
  mature double positive cells

• How do we generate diversity in T cell receptors?

  Somatic recombination. all resions held lots of gens and combine in a random way.

• Which selection of T cells is in the thymus?

  Positive selection: T cells that not bind to a MHC molecule will die
  Negative selection: select those T cells that are able to recognize self antigens, to avoid auto-immunity.

• What stages are there in B cell development?

  Repertoire assembly: generation of diverse and clonally expressed B cell recpetors in the bone marrow
  Negative selection --> alteration, elimination or inactivation of B cell receptors that bind to components of the human body
  Positive selection -> promotion of a fraction of immature B cells to become mature B cells in the secondary lymphoid tissues
  Searching for infection in the lymph node and blood and secondary lymphoid tissues
  Finding infection: activation and clonal expansion of  B cells by pathogen-derived antigens in secondary lymphoid tissues
  Attacking infection : differentation to antibody-secreting plasma cells and memory B cells in secondary lymphoid tissue

• How is the structure of an immunoglobulin/antibody molecule?

  Heavy chain = 4 domains
  Light chain = 2 domains
  Heavy chains have disulfide bonds
  one antibody can recognize two different type of epitopes at the Ntermini

• What is the different of T cells and B cells recognizing the pathogen?

  B cell receptors recognize the native pathogen with their antibodies or B cell receptors
  
  T cell receptors recognize peptide antigens produced by degradation of pathogen proteins by dendritic cells. A fragment must be presented by an MHC molecule

• How is the process of a MHC class I and II molecule presenting an antigen?

  Antigen outside of the cell, the antisgen will be in an endosme and in the cell fisue with a lysosome. This lysosome contains enzyms that will degrade in the antigen. 
  Golgi aparatus makes the peptides at the class II molecules go to the outside
  
  Virusintected cell. Peptides are generated in the cell itself. The golgi apaprates will encouter MHC class I molecules, which will be loaded with those pepstides and trnasposrted to the sruface.

• What kind of pathogens do MHCI molecules binds, MHC II molecules? what is the exception?

  MHC I: peptides derived from protein synthesis by the presenting cell
  MHC II: peptides derived from endocytosed proteins (extracellular)
  Exception: cross-presentation of endocytosed proteins on MHC class I molecules.
  Cancer cells present antigens antigens in class

• What is the role of a dendritic cell?

  Dendritic cells pick up antigen, transport it to the draining lymph node, where they stimulate adaptive immunity. 
  Some molecules will be degraded by the dendritic cells, other molecules will activate dendritic cells.
  
  The dangerous signal indcated that we need the immune system.
  The dendritic cell is then able to migrate through the lymph vessels through the lymph node.
  
  So  a dendritic cell is thanks to the pathogen able to:
   - migrate to the lymph node
  -  in creased the expression of co-stiulatory molecules