Chapter 11

Immunological Memory and Secondary Immune Response

  • Relies on:

    • antibodies

    • long-lived memory T/B cells

      • each activated T/B cell undergoes asymmetric division to give one effector cell and one memory cell

    • secondary responses are faster, better

  • Why secondary responses are faster and better

    • memory cells outnumber pathogen specific naive lymphocytes

      • antibodies formed during primary immune response prevent reinfection for several months after disease

    • memory cells activated quicker

      • pathogen-specific memory cells more abundant and make better antibodies than naive B cells

      • somatic hypermutation, affinity maturation

      • isotype switching already happened

    • memory cells can migrate to non-lymphatic tissue and respond sooner

      • can be activated at SOI

    • activation of naive B lymphocytes is inhibited

      • naive B cell activation suppressed

      • memory antibodies turn off naive B cells

Vaccines

  • 2 ingredients

    • target antigen(s)

      • provides signal 1 for T cell activation

      • many vaccines are combination vaccines that contain multiple antigens

    • adjuvant

      • chemical that stimulates inflammation

      • provides signal 2 for T cell activation

      • sometimes not needed if pathogen is intact enough to stimulate inflammation on its own

Viral Vaccines

  • “killed” or inactivated viral vaccines

    • virus inactivated by heat/chemicals (formaldehyde)

    • many antigens denatured

    • adjuvant required to stimulate inflammation

    • easy, add head and/or chemical treatment

  • “live” or attenuated viral vaccines

    • virus not able to replicate in our cells (genetically modified), but antigens are intact

    • very strong immune response stimulated

    • no adjuvant needed

    • requires time and precautions

  • subunit vaccines

    • only antigenic part of virus used in vaccine

    • avoids the need to cultivate massive amounts of deadly virus

    • adjuvant needed

    • requires a lot of background research and time to develop

  • Polio vaccine tragedy

  • mRNA (Pfizer and Moderna)

    • mRNA sequence for part of spike protein

    • our cell produces spike protein

    • our immune cells respond

    • PEG in both, can cause severe allergic reactions

  • protein subunit vaccine (Novavax)

    • spike protein plus adjuvant

    • fraction A and fraction C of quillajusaponaria molina extract

  • viral vector vaccine (J and J)

    • adenoviral vector carrying DNA instructions for part of spike protein

      • we’re already exposed to adenovirus and will attack and eliminate

    • contains large dose of viral vector, blood clot risk

  • Covid problem: memory doesn’t last long, we don’t know why

Bacterial Vaccines

  • killed

    • common strategy for bacteria

    • heat/chemicals

  • live (attenuated)

    • small number of them

    • BCG used for TB in Europe

      • salmonella typhi vaccine

      • 20-50% causes side effects

  • subunit

    • bacterial toxins are common antigen targets of neutralizing Ab’s (ex. DTP)

    • capsular polysaccharides (pneumococcus, menigococcos, HiB, etc.)

    • conjugate vaccines enable high-affinity Ab’s to be made against carb antigens

      • use carrier protein attached to small carb antigen