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Flashcards in Lecture 5 Deck (27):

What are the two differentiations of B cells 

  1. Plasma cells 
  • ​Produces low affenity antigen specific antiboides 

    2.  Memory B cells

  • produce high affinity antigen-specific antibodies
  • These are long-lived plasma cells


What are the 5 main antibodies 

  • IgA 
  • IgG
  • IgM 
  • IgD 
  • IgE
  • Each have a specialised function - Classified according to their heavy chain 


What is the dual biological function of Antibodies 

  1. Varaible regions - Recognition function
  • Binding of antigen is mediated by variable regions

    2.  Constant regions - Effector function 

  • Clearance mediated by constant region interacting with effector molecules
  • Effector molecues = Complement and Fc receptors 


Describe the structure and role of IgM

  1. Monomer - Memebrane bound form serves as a B cell antigen recptor 
  • Function: B cell activation 

​     2.  Pentamer - present in plasma and scretory fluids 

  • first antibody produced during an immune responce 
  • Function: Agglutination and complement activation 


Describe Agglutination

  • When an antibody cross-links multiple antigens producing clumps of antigen
  • Specific antigen binding to IgM and IgG
  • Enhances clearance of pathogen by phagocytosis 


How is the classical pathway of complement activated 

  • Initiated by specific antigens binding to IgG or IgM antibodies 
  • leads to conformation change in the heavy regions of the antibodies 
  • Exposes multiple binding sites for C1 complement protein - which is the first component of the classical pathway 


Describe the structure and function of IgG antibody 

  • Most abundant antibody in serum - 80%
  • This antibody is produced during a secondary/memory immune responce ​​
  1. Functions
  • •Agglutination
  • •Complement system activation
  • •Foetal immune protection
  • •Neutralisation
  • •Opsonisation
  • •Natural Killer cell activation


How does IgG take part in foetal immune protection 

Transport via placenta directly into foetal blood circualtion 


Describe neutralisation by antibodies 

  • For specific antigen binding to antibody- protective mechanism
  • IgG  and dimeric IgA
  • Function:
  1. Protects pathogen from infecting host
  2. Prevents pathogen toxins from disturbing normal cellular function


Describe opsonisation by antibodies 

  • Antibody coats spefici antigens
  • Constant region of heavy chains Bind to Fc receptor on macrophage 
  • Enhance phagocytosis


How do antibodies enhance NK cell activity 

  • Infected host cells or apoptotic cells express 
  • IgG antibodies on surface
  • Binds to Fcy receptor on Natural killer cells
  • Leads to cell killing and release of IFNY which enhances phagocytes 


Describe the structure and function og IGD antibodies

  • Membrane bound form - B cell activation
  • secreted form in low levels in plasma and function is not well understood


Describe the structure and function of IgA antibodies 

  • Second most abdundant
  1. Monomeric form - in serum - B cell activation
  2. Dimeric form - found in secratory fluids 
  3. Secreted IgA: 
  • ​Neonatal defence 
  • Neutralisation


Describe the structure and function of IgE antibodies 

  • Tiggering allergic responces
  • Asthma, allergy anaphylaxis 


When are the different antibodies produced during the adaptive immune responce 

  • IgM is the main produce early one in the reponces to antigen
  • IgG and others are produced later on


How are antibodies of the same specificity, but different Ig classes produced? 

  • During B cell activation, B cells can change the gene segments of heavy chain constant region
  • process if induced by specific cytokines 


What are the effector functions of activated CD4+ T cells


What are the different T effector cells and whats their function 


How do T effector cells stimulate other Immune cells 


How do Effector T cell help T cell responces?

They secrete Interleukin-2 (IL-2) – this a cytokine which stimulates proliferation and differentiation of antigen-activated T cells (and antigen-activate B cells)


How do effecto T cell stimulate macrophages 

  • Effector TH1 cells migrate from secondary lymphoid tissues into infected tissue sites.
  • TH1 cells are re-activated by tissue-resident macrophages in an antigen-specific manner
  • TH1 cells express co-stimulatory molecules (e.g. IFNy) that hyper-activate macrophages, enhancing their killing activities and pro-inflammatory cytokine production.


How do Effector T cells help B-cells

  • Protein antigen bound to BCR is internalised by the B cell
  • Antigen is degraded and peptides are presented on the B cell surface in complex with MHC-II
  • Effector TFH cells move into B cell zone of the lymph node where they are re-stimulated by B cells in an antigen-specific manner and start to express co-stimulatory molecules
  • Re-activated effector TFH cells stimulate the B cell to clonally proliferate
  • •The re-activated Effector TFH cells secrete cytokines that further activate the B cell and stimulate the Germinal Centre response


What are the germinal center responces 

  • B cell proliferation
  • Differentiation into plasma cells
  • Differentiating into memory B cells
  • Ig Heavy chain class switching
  • Generation of high affinity antibodies


What are the effector functions of CD8+ T Cells 

CD8+ cells → Cytotoxic T Lymphocytes (CTLs)
    → Kill infected host cells


How do CTLs kill infected hosts

Exit lymph nodes - enter site of infection - recognise and kill infected tissue cells in an antigen-specific manner


Describe the killing process by CTLS

  1. Release of lytic grangules containing 
  • ​Perforin - forms a pore in target membrane 
  • Granzyme - Serin proteases triggers Apoptosis
  • Granulosin - Induces apoptosis

​     2.  Fas-ligand mediated killing 


Restoring immune system back to Homeostasis