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Flashcards in Lecture 4 Deck (25):

How long does the adaptive system responce last for 

Days - Weeks


Does does the adaptive immune responce carry out recognition

Via antigen : antigen receptros 


Where are B and T cell produced 

Bone marrow 

  • B cells mature in bone marrow
  • T cells mature in the thymus 


What are the 2 types of T-cells 

  • CD4+ T cells - regulate immune system
  • CD8+ T cells - kill virally infected cell bodies 


That is the difference between PAMPS and Antigens 

  1. PAMPs
  • ​Non specific recognition 
  • Limmited number of PAMPS that are common to many different pathogens 

    2. Antigens

  • Specific recognition 
  • Millions of different ones that are unique to individual species
  • Individual B and T cells express ony one specific receptor for an antigen 

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What is the B cell antigen receptor - BCR

Memebrane bound antibody - IgG/IgD 

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Explain the T cell antigen receptor

Membrane bound alpha,Beta Heterodiamer 

  • Alpha chain 
  • Beta chain 

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Describe antibodies 

  • Produced by B-cell in responce to an antigen
  • Bind specifically to that antigen
  • Are expressed on surface of B cells and also secreted by B cells as soluble protiens
  • Provide defence againts ectracellular pathogens - Bacteria, viruses and toxins


Desctibe the structure of antibodies 

  • 2 Ig heavy chain  and  2 Ig light chain polypeptides held together by disulphide bonds 
  • Each Ig heavy chain and light chain contains: 
  1. Variable region
  2. Constant domaine 

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Why can antibodies have different reachs 

Flexible at hinge 


How can different antibodies exist if they have the same structure

Have different Ig heavy chain regions 

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What are the different types of heavy chains and antibodies 


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Which part of the antibody is the antigen binding site 

Hypervariable regions of Ig light and heavy chains combine to form antigen binding sites

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Describe the TCR and its binding site for antigens 

  • Membrane bound heterodimer of alpha and beta chains 

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How can the immune cell recognise millions of different antigens 

  1. B cells -•Antibody heavy and light chain proteins are encoded for by segmented genes in the germ-line genome of haematopoietic stem cells
  • Randome rearrangment in these gene segments occur as B-cells evelop 

    2.  Similar randome rearrangement of TCR a/b chain gene segments occurs in developing T cells

  • Gives rise to hugly direverse B and T cells 
  • This means theres is potential for auto-reactive cells 

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T and B cells elimination of pathogen process

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Where does the adaptive immue responce occur 

Secondary lymphoid tissue 

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How do nieve B and T cells enter lymph nodes


Transendothelial migration 

  • Enter lymph nodes from High endothelial venules (HEV)
  • If after several days they dont encounter any pathogen they return back to blood system via Efferent lymphatics 

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How do antigens enter the lymph nodes?

  1. Debris of pathgens are released by phagocytes 
  2. Inflammatory cytokines (TNFa) stimulate immature, tissue-resident Dendritic Cells ►expression of co-stimulatory molecules
  3. .Dendritic Cells recognise (PAMP:PRR) and phagocytose pathogen-derived particles and antigens
  4. Dendritic cells ingests and display small peptide on surface with a MHC complex 
  5. Pathogen debris, antigens and mature denritic cells move to local draining lymph nodes 
  6. Enter lymphnodes via Afferent lymphatics 


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How are T cells activated 

  1. T cells can only recognise peptide antigens presented to their TCR by MHC molecules 
  2. Also known as HLA molecules - able to present many different peptides 
  3. Encoded by highly polymorphic genes

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Describe the two classes of MHC molecules 

  1. MHC class 1 - presented on all nucleated cells
  • Present peptide antigens to CD8+ T cells 

​    2.  Class 2 MHC - presented on professional Antigen presenting cells

  • Dendritic cells, macrophages, B cells
  • Present peptide antigens to CD4+ T cells 


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What are the 2 signals required for T-cell activation

  1. Antigen specific stimulation signal 
  • Denritic presents MHC peptides to the TCR of T cellls

    2.  Co-stimulatory signal 

  • B7 molecules : CD28 on T cell 

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Whats the function of stromal cells in B-zones 

Trap opsonised antigens

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How do B-cells get activated

they dont need to be presented with MHC peptide 

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What happens to activates B and T cells

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