immune processes

• all nucleated cells have the ability to present

  MHC-I
• MHC are membrane bound

  glycoproteins
• CD8+ cytotoxic T cells (CTLs) recognise MHC-I and antigen presented by 


  infected cells
• CD4+ T helper cells recognise MHC-II and antigen on 


  antigen presenting cells
• dendritic cells

  • phagocytes
  • move from site of infection to lymphoid tissues
  • display processed antigen to naive helper T cells
  • important in triggering primary immune response
• macrophages are important for

  secondary immune response
• 3 immune processes

  • inflammation
  • humoral mediated immunity
  • cell-mediated immunity
• humoral immunity

  • B cell mediated
  • antibody-antigen mediated
  • phagocytosis and complement-mediated killing
• cloning of lymphocytes driven by antigens is


  clonal selection
• humoral response

  • macrophage or dendritic cell phagocytoses pathogen
  • Breaks down pathogen
  • Antigen complexed with MHC-II protein, binds with CD4
  • Helper T cell activated
  • B cell phagocytosed BCR and antigen, presents antigen on MHC-II
  • Helper T cell recognises antigen presented by B cell
  • Cytokines from activated helper T cell fully activate B cell
  • B cell activated to produce clones of plasma cells and memory B cells
  • Antibody production from plasma cells
• plasma cells are antibody secreting cells
• antibodies can opsonise, neutralise, precipitate and agglutinate
• antibody can cause complement fixation
• 3 complement pathways 


  classical, lectin and alternative
• antibody-activated pathway is the classical complement pathway
• all complement pathways end with the formation of membrane attack complexes
• over 30 complement proteins
• C1 pathway involves 


  C1r, C1s and C1q
• cell-mediated response

  • CTL
  • MHC-I antigen T cell receptor
  • cytotoxic T cell mediated killing and humoral response, activation by Helper T cell
• cell-mediated response steps

  • infected cell presents antigen on MHC-I to cytotoxic T cell
  • T cell receptor binds to presented antigen
  • CD8 binds to MHC-I
  • CTL cell is activated
• perforin 


  forms pores in target cell membrane
• granzymes


  initiate apoptosis in target cells
• cytotoxic cells do not phagocytose
• T cells don't present an

  antigen
• immune response

  labels

  A) antigen presenting cell

  B) helper T cell

  C) B cell

  D) plasma cell

  E) memory B cell

  F) cytotoxic T cell