• Question: How many pathogens can 1 memory cell remember? And does venom and poison have pathogens?

    Asked by Meg D to Samuel, Nikolai on 13 Mar 2015.
    • Photo: Nikolai Adamski

      Nikolai Adamski answered on 13 Mar 2015:

      First part of the question:
      Imagine that pathogens have locks that guard them, while memory cells have keys to “unlock” the pathogen. The human immune system can create an essentially infinite amount of keys. Each memory cell only gets one key (and that key doesn’t change anymore), so in most cases will only be able to work against a single pathogen. There is however the odd chance that two pathogens have the same lock, so the same memory cell could in theory be effective against several different pathogens (provided they have the same “locks”).
      Second part of the question:
      Venoms and poisons are chemical substances that have some sort of harmful effect on an organism. The exact effect depends on the poison/venom, the dose of the poison/venom as well as the size and anatomy of the victim. For example, many snakes are poisonous, but while most of them can kill a mouse with a single dose, a human could survive the same dose of poison as it is being diluted in our bigger bodies (again, this depends entirely on the type of poison).
      Some species however use pathogens (e.g. bacteria) as a kind of slow poison. The komodo dragon for example has a large amount of pathogens in its saliva, which often leads to a fatal infection in the bitten victim. But other komodo dragon species are also poisonous in the classical sense (chemical poison).

      A little fun fact on poisons: The Botulinum toxin (produced by a bacteria)causes paralysis of muscles. It is also the acting ingredient in Botox cosmetic treatments. The poison paralyzes facial muscles, thus preventing formation of wrinkles. 🙂

    • Photo: Samuel Ellis

      Samuel Ellis answered on 16 Mar 2015:

      Nikolai has answered this question thoroughly, so I won’t say too much. In general memory cells are specific to a particular antigen (which is anything the immune system detects as foreign, usually something like a protein on the outside of a bacteria), and as we are exposed to things we develop a wider range of immune ‘memory’. This is obviously the science behind vaccines, where safe versions of pathogens are administered to let our immune system easily learn to target it in the future.

      Pathogens are living organisms which harm us, so things like bacteria, viruses, parasites and even certain fungi. Venom and poison on the other hands are naturally-produced chemicals, and usually come from bigger creatures like snakes, frogs and scorpions for example. Many pathogens do secrete substances which harm us however, which we often call toxins. They have a range of effects, but are often involved in either damaging our cells to help pathogens stick/invade, or attacking our immune system to protect itself.

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