How does the immune system work?

May 11, 2005 1:27 PM

The silver lining to colds and flus has always been that at least my immune system is better for it, and I’ll be less likely to catch the next thing. However, I’ve caught 3 colds (or something- they were all different, and none were serious) this year and it’s only May! In the past I’ve caught maybe one thing a year. Does your immune system stop improving as you get older? Why do old people get sick more easily? And how old are you when that starts? And how possible IS it to reinfect yourself with the exact same virus or bacteria? Once you’ve had something, wouldn’t your immune system just whomp it the next time it came by?
posted by small_ruminant to health (20 comments total)

Been stressed lately? A lot of studies out there show that stress makes it harder to kick an infection. And you may not develop an immunity the first time around.
posted by IndigoRain at 1:51 PM on May 11, 2005

Maybe stress. I don't take vitamins or anything, but I eat well. Do vitamins really do much if your diet's alright? How 'bout exercise?
posted by small_ruminant at 1:55 PM on May 11, 2005

I've noticed that there are some things going around this year. I, too have pretty much only gotten sick once a year, if that, in the past, and have been laid low about three times this year already. Coincidentally, everytime I've been sick, people have been remarking to me - "hey, have you got that thing that's going around?".

Must be all the antibiotics in the water.
posted by Caviar at 1:59 PM on May 11, 2005

So at what age does your immune system start falling apart instead of improving?
posted by small_ruminant at 2:07 PM on May 11, 2005

I think it's just this year - I too usually get sick once a winter but this year I've gotten sick every other week. I've taken to calling this "The Winter of a Thousand Sicknesses." Must be all kinds of weird flu/cold variants out there.
posted by Dallasfilm at 2:38 PM on May 11, 2005

I'm going to second caviar here and dallas here -- the norm has always been one illness, if any, for me but I just got over number four of the season.
posted by incessant at 2:48 PM on May 11, 2005

Vitamins are no good once you have an infection - you're just feeding the bacteria/virii (yeah, I know it's viruses).

Getting a cold, then recovering from it, does not necessarily protect you from the next one. It depends on which epitope (shape of molecule from virus/bacteria) that your immune system recognized. You'll be immune from further infection by the same strain (unless you've been really stressed out and your immune system is rendered into goo), but that doesn't mean you're protected from the next strain (ie., one year's flu vaccine may not work for next years [or even this year's] flu strain).

As for the immune system, the very young have poor immature immune systems. By adulthood (20-30-ish) the immune system is pretty much at it's peak.

Now, there are 2 'kinds' of immune responses. One is innate (fast acting, attacks everything) and the other is adaptive (slower acting, only attacks one kind of thing - but only after it recognized it). If you have great innate immunity, then you might not even get to adaptive immunity because the threat (bacteria/virus) is already gone. If not, then the innate immunity eventually recruits the adaptive immunity.

As one gets older, the adaptive immunity loses it's ability to recognize new epitopes (shapes from bacteria/viruses) but the innate immune system gets a little better and usually manages to compensate. However, the adaptive immunity is still around and can recognize (most) of what it's been exposed to before and deal with it.
posted by PurplePorpoise at 2:59 PM on May 11, 2005

A google scholar search turned up this article. To paraphrase:

- There are two forces at work here: Normal decline in immune function, and secondary immunological changes.
- "Secondary immunological changes are due to underlying diseases and various environmental factors, including diet, drug intake, physical activity, etc."
- You can't change the first one, so you better get to work on the second.

Aside from that, I don't see anything wrong with disinfecting heavily used surfaces and washing hands. Water, or preferably soapy water, is 99% as effective as antibacterial soaps. But use 'em if you gotta. I have read that meditation works. Personally I hang upside down because I feel like it gets my lymph system moving. Or something.

So at what age does your immune system start --whoa there, let's not get carried away.
Your immune system probably stopped improving markedly by age 18. I would personally prefer a little less immune function when it comes to having penecillin in my body.
posted by MarkO at 2:59 PM on May 11, 2005

I'm hoping you're right, and it's just this year.

Does anyone have any stats? Are we warming up for a plague? (Most my family got wiped out in the 1918 one- does that mean I ended up with some inherited immunity?)

And does getting multiple colds this year mean that next year I'll get fewer, (if they aren't all brand new ones)?
posted by small_ruminant at 2:59 PM on May 11, 2005

I didn't see your post MarkO- thanks.

What do you mean by this?

I would personally prefer a little less immune function when it comes to having penecillin in my body

I'm allergic to most antibiotics so I'd like to keep my natural immune system healthy.
posted by small_ruminant at 3:02 PM on May 11, 2005

As long as you have a normal number of T-cells and B-cells (assuming your B-cells and T-cells are normal), your immune system continues to learn how to respond to new invaders your entire life.

When your body encounters a new pathogen, the T-cells that you already have that are specific to the new pathogen begin to clone themselves. You end up with a large number of cells that can produce antibodies to neutralize the pathogen and a small number of memory cells that stick around in the body to mount a response if you get a secondary exposure to that same non-self antigen. During that secondary exposure, thanks to those memory cells, your body mounts a secondary immune response that is swift and devastating. Where the primary response may take a week or more, the secondary response can take hours or only a couple of days.

I don't know much about how the immune system ages, but I suspect that the universal good diet and exercise make a huge difference in how fast your immune system goes downhill.

On preview, a lot of this was already covered, but maybe I got a little extra in there.
posted by Elsbet at 3:08 PM on May 11, 2005

Oops. I really need to learn to scroll up while I'm previewing. PurplePorpoise pretty much answered my questions. Thank you!

(and thank you, too, Elsbet!)
posted by small_ruminant at 3:39 PM on May 11, 2005

While your immume system does learn, so hopefully you only get a cold once, there are unforunately hundreds of different cold virus varients - enough for a multiple new ones every year for your entire life, and they'll keep on changing too.

I haven't been sick for years and this year I've come down with something, so I third that this has been an usual year for me as well.
posted by -harlequin- at 4:29 PM on May 11, 2005

Elsbet - after about 50 years, the clonal T and B cells take up so much "space" (it's an idea that adequately explains a lot of observed phenomenon but it's been poorly characterized - I have a paper somewhere if you're interested) that the number of naive T & B's (which are then able to recognize as-yet-unencountered epitopes and mount a response) are essentially reduced. So instead of being able to mount an effective adaptive response, elderly people are susceptible to the direct effects of pathogens and will mount a greater innate response (fever, &c) and thus suffer a higher mortality to infection.

With intracellular viruses (and bacteria), though, natural killer cells (and phagocytic cells) are important, too. Not sure how much research has been made with those populations and aging.

A lot of being "sick" isn't so much the virus or bacteria having it's way with you (some of it is, especially viruses that hijack your cells to make more virus), but your body is responding to the virus/bacteria by raising your temperature and making you ooze mucus, so it's not a "bad" thing to have a some symptoms of being sick.

small_ruminant - cheers bud, if you find yourself getting sick a lot, like MarkO sez, wash your hands a lot, avoid scratching/rubbing your eyes, and get more sleep! Exercise can also raise your white cell count (and also does a lot of other good things for you).
posted by PurplePorpoise at 4:37 PM on May 11, 2005

So, PurplePorpoise, when you're washing your hands a lot, is it simply to keep from infecting everyone else? Or does it help you personally, too?
posted by small_ruminant at 4:53 PM on May 11, 2005

It helps you. A lot. Face masks, otoh, only help protect other people from you. A lot of micro-organisms use mucous membranes (eyes, nose, mouth) to get inside of you. Rhinovirus (literally, nose-virus) - which make up the predominant virus that causes colds - can only get inside of you through receptors in your nasal mucous membranes (I can't remember if this was a joke or if this is actual data - but rhinovirus makes your nose itch so you scratch it, and thus gets to your nasal membranes).

Normal soap can both kill bacteria as well as help get them unstuck from your hands. In some cases it can also lyse (break apart) viral capsules, some of which can be very sticky. Antimicrobial/antibacterial soap typically have triclosan (a small molecule that inhibits lipid synthesis in a wide variety of micro-orgs - make it so that they can't grow) or (liquid soaps) have isopronal/ethanol which penetrates into the micro-orgs and also inhibits growth/induces death. However, the anti-microbials don't usually stay on you long enough to actually do anything.

I've learnt to 'surf' public transit hands-free so I minimize touching anything. Public telephones are teh suck for pathogens. Sharing smokes/joints, tonsil wrestling (especially with someone you haven't swapped microbes with before), spending lots of time in office buildings with poorly designed ventilation, or just being in a confined space all increase the risk of you catching something.
posted by PurplePorpoise at 5:50 PM on May 11, 2005

I used to get sick quite a bit when I was younger. Since then, I've had a job in public health in Long Beach, CA and I'm pretty sure that if you stand next to me, my immune system will attack any viruses or bacteria in your body.
posted by kamikazegopher at 7:11 PM on May 11, 2005

You need more sleep! That's the bottom line! Worked for me. Get enough sleep every night, and if you feel a cold coming on, sleep 1.5 times as much.
posted by knave at 7:24 PM on May 11, 2005

kamikazegopher - lol, I had an oboe teacher who was pretty much the same thing. When teaching oboe, you also teach/fix reeds - this guy has been exposed to *so many* different microbes I swear that he had antibodies in his saliva that would cure his student's illnesses; kind of like how immunoglobin A's in breast milk help protect breastfeeding infants...
posted by PurplePorpoise at 8:39 PM on May 11, 2005

Thanks- I learned a lot!
posted by small_ruminant at 9:44 AM on May 12, 2005