If you catch e.coli or salmonella once, shouldn’t your body learn new more efficient ways to combat it for the next time it gets in?
In: Biology
Some things are just poisonous no matter how many times you encounter them. A disease might be something your body’s immune system can learn to recognize and combat more efficiently, but if you drink bleach your body isn’t going to get better at handling bleach. There is nothing to learn there, it is just bad.
The problem with bacteria that spoil food is not usually the bacteria themselves but their poisonous poop. This is also why you can’t just cook spoiled food and make it better by killing all the bacteria. The poison is still poison.
Body combats them quite fine. Problematic bacteria just grows-multiplies very quickly and overwhelms the immune system. That’s what makes them dangerous.
Also, many parasites are often too big and complex for body to do something about them. So foodborne problems come from quite particular bacteria and parasites. Rest body can deal with.
Our bodies are constantly fighting off bacteria and viruses – there’s bacteria on everything and your immune system works 24/7. Diseases that we worry about are the few rare things that are tough to fight off
A part of our immune system is to make specific B-Cells which produce antibodies which specifically target and pummel the bacteria/virus that infected you. These B-Cells persist even after the infection, so you are essentially immune against the bacteria/virus with that specific DNA. The problem is that bacteria/viruses reproduce so much (tens of thousands in just one infected human) that they mutate constantly and get better at infecting and persisting in humans. But these B-Cells only prodice antibodies against the bacteria/virus 50000 generations back. So the body has to activate and make new B-Cells. But then the bacteria/viruses mutate, and so on.
It’s not the bacteria it’s the toxins they leave behind, you can’t build immunity to toxins
Some cases, like botulism, are due to toxic waste products of certain bacteria, and it’s a straight up nerve toxin
With food born illnesses get in your gut quickly through eating before your adaptive immune system (antibodies and killer immune cells) is able to react, assuming you have antibodies in the first place. You eat some some food and a few hours later that food with the bacteria is in your gut. I am making some general statements here but different pathogens can behave differently. But your typical food poisoning lasts a day or two. Most of that is handled by you innate immune system and the bacteria remains in your gut and is not floating through your blood stream. Your innate immune system is “non specific” meaning it recognizes threats “generally” not specifically. For example your innate immune system can detect the presence of some bad bacteria of different types. and there are many types of bacteria that would set off the same reaction. Similar with different viruses of certain types. Sort of like your innate immune system says “I need to act because there is a bad bacteria in here, I don’t know what it is, but that doesn’t matter because my response is the same and I can do this before the adaptive immunity has time to develop antibodies which takes several days.” Your antibodies are part of your adaptive immunity and is “specific”. You make antibodies to exactly that particular strain of bacteria or virus and those antibodies may or may not work on other strains of the same type of bacteria or virus for example.
So the E. coli or whatever gets into your gut a short time after you eat it, cells in your digestive tract have receptors that are “sensors” for things found in many bad bacteria. The innate immune system has those receptors (or sensors) triggered which ends up sending some warning signals to surrounding cells and it reaches part of your brain. Your brain will recognize this signal as bad and send a signal to your digestive track to “get that stuff out of there right now”. So you may start getting diarrhea which flushes the contents of your lower gut to wash the bad stuff out. You may also start vomiting which is removing the bad stuff from the other direction out your mouth. Basically flushing your stomach by puking. Depending on the pathogen this may be enough to get it out and get rid of it over the course of a day or two. If successful those sensors in the digestive tract will no longer detect the bacteria, will stop sending the warning signals, that will get to the brain and the brain will send a signal back to stop flushing out your system. Typical mild food poisoning lasts one to two days.
This assumes the particular pathogen has not entered your tissues and start to grow and invade there. If it does that then your adaptive immune system will also get involved. If you have antibodies already to the pathogen they will get produced pretty quickly in a day or so and typically the pathogen can be killed off pretty quick. If you don’t have antibodies to the pathogen then your body need to make them and this can take about a week. Your innate immune response may still be flushing things out till those antibodies and killer immune cells are produced. In this scenario you will likely be sicker for longer, maybe 7 days. That is the most straight forward scenario.
Some pathogens just remain in the gut and start growing there and the innate response is the main one. (There is some adaptive response in there but it is kind of complex, and the innate response is the main one for 1-2 day food poisoning so keeping it ELI5 here).
Worth noting if a pathogen does invade your tissues, you make antibodies and killer immune cells to that specific pathogen. But you might get that same pathogen again later and the antibodies don’t work because there can be numerous strains of that bacteria that may not be recognized by those antibodies from the previous infection. Or a pathogen may change what it looks like while it is growing in you to evade the immune response. These things have developed ways to thwart that immunity. Sometimes it is as simple as one type of bacterial pathogen just has lots of different types that “look different” as far as antibodies are concerned and you need to make new ones. There is no one answer to this and you have to get into details of a specific pathogen to comment on how that one may thwart the immune system and bacterial have come up with lots of clever ways to do that.
The short answer is we can develop immunity to these but they change and evolve, or there is a lot of different types that can re-infect you later etc. A lot of time that reliable innate immune response is enough and just flushing it out does the job and you feel sick for a day or two.
This is a very general, simplified answer for some of the more typical food poisoning people experience.
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