22- memory

• Memory


  • Relies on few pre-existing clonally expanded cells to provide a more rapid, specific, and larger response
  • Does not require constant exposure to pathogen
  • The cells will just stay alive
• T Cell Memory

  2 types of memory cells: Activated naïve (new effector) cells and Circulating Cells
• Central Memory Cells: TCM

  • Stay in secondary lymph organs
  • Good to stay in the same place as initial infection as that is where it is likely to happen again
  • Long lived
  • Can derive from effector cells
• Stem Central Memory Cells TSCM

  • Essentially THO
  • Rare, differentiate into many effector types
• Effector Memory Cells: TEM

  • Circulate through periphery
  • Not so long lived
  • Takes energy to keep them around
• Resident Memory Cells: TRM

  • Stay in specific peripheral tissues
  • First line of defense
  • Can appear within 3 days
  • Need IL-7 and IL-15 and weak MHC interactions to stay alive and keep proliferating
• CD8 Resident Memory Cells


  • Tend to have more and they live longer
• B Cell Memory


  • Faster (no lag) and stronger
  • Can undergo more somatic hyper mutation so with each infection they keep improving
• B Cell Memory Properties


  • Don't express IgD, generally IgG predominant
  • Generally in marginal zones
• Secondary, Tertiary, Etc. Responses

  1. Guided almost entirely by memory cells

  2. They go first and prevent new naïve B and T cells from reacting

  3. Its a waste of effort to activate the new cells if you don't need to
• Negative Regulation of B Cells

  • ITIM inhibitory
  • SH2 (SHP-1, SHIP): shifts cells below threshold
• Features of Adaptive Immune Responses

  • Specificity
  • Diversity
  • Memory
  • Specialization
  • Self-limitation
  • Non-reactivity to self
• T dependent antigens


  Not as strong of a response but have memory
• T independent antigens


  Not so much memory development but act fast and produce lots of IgG
• Independent B cells: B1 cells

  • Produce natural antibodies
  • Secrete IgM, no isotype switch
  • Don't generate memory
  • Express CD-5: T cell activation marker
  • Present in high numbers in fetus and neonates: recognise ABO blood group