If the immune system has finite resources, would reducing the lifetime drain on those resources by infectious diseases delay the age at which we can expect get cancer? For example, curing the common cold and/or developing a universal flu vaccine.
"If the immune system has finite resources, would reducing the lifetime drain on those resources by infectious diseases delay the age at which we can expect get cancer?"
I would wager the opposite is true. Body systems maintain themselves and their fitness and function through use.
The obvious examples are bone and muscle tissue that become stronger through stress but are you aware that breast cancer incidence is strongly, negatively correlated to frequency and duration of breastfeeding ?
The immune system is also a bodily system and I would be surprised if it did not, also, strengthen itself and maintain its function through stresses and use.
"For example, curing the common cold and/or developing a universal flu vaccine."
Be careful what you wish for ...
We "cured" hard physical labor and traditional life patterns with lots of walking and standing. How's that working out for us ?
> We "cured" hard physical labor and traditional life patterns with lots of walking and standing. How's that working out for us ?
I'll bite -- terribly. Many of the millennial generation and younger are actively starting to revolt against these sedentary lifestyles. It's why fitness and fitness culture is so marketable these days, much more than I remember. I think the studies that came out showing the millennial were the first generation since the industrial revolution to have a decreased life expectancy versus the prior generation was a real wakeup call.
Yes, not having to do physical labour is better than being forced to do physical labour as a worker or peasant. The new problem for most people is how to eat less and get a little exercise. But this is a better problem.
I like rsync's main point though about the immune system maybe requiring usage and callibration (gojomo mentions the hygiene hypothesis). Perhaps one day we'll determine the precise amount of these required (if any) for us to be healthy without being bothered by too much sickness.
It would be interesting if the cure for/long delay of cancers was in an early and vigorous exercising of our immune system with respect to viruses---if the solution was a kind of continual vaccine for colds and viruses that needed to be updated regularly. Like an immune system gym/daily workout. I wonder if there is any research being done on that end of things.
Via mechanisms similar to either the hygiene hypothesis or hormesis, it's possible those might backfire. This is highly speculative, but:
* the hygiene hypothesis suggests that allergies and auto-immune disorders can arise from having insufficient immune-system challenges, especially when young. Lacking the calibration from an 'expected' or 'optimal' level of dirt/allergens/infectious-diseases, the immune system starts doing unwanted self-destructive things.
* hormesis is the observation that almost everything bad for you also turns out to be good in very-tiny exposures – radiation, poisons, cancer-causing chemicals, etc. It's as if tiny doses trigger beneficial self-repairs to occur even beyond the direct damage received, even as larger doses overwhelm that mechanism.
Removing mild, survivable challenges from the environment could thus leave the immune system less 'tuned' for the full spectrum of challenges it faces (like clearing early cancers). It's an adaptive dynamic system with nonlinear effects, not a simple pool of fixed exhaustible capability.
"Removing mild, survivable challenges from the environment could thus leave the immune system less 'tuned' for the full spectrum of challenges it faces"
Exactly. You want to protect people from, say, Rubella ... but I think we should proceed with caution with things like the cold and the flu ...
And historically, reducing the burden of infectious disease already has increased life expectancy and reduced/postponed incidence of age-related disease:
I'm not sure 'finite' is the right way to think about it. I'd be more inclined to think of infections acting to 'Exercise' the immune system, similar to how jogging keeps your heart healthy, rather than using up a limited number of immune cells.
This is not known, but it's a great question. As usual, probably some genetic but also mostly epigenetic factors.
There's a huge variability in terms of your thymus (the organ that produces new T cells) getting switched off after your mid 20s. For some people its almost immediate. For others, it takes many decades: https://insight.jci.org/articles/view/93739/figure/5
Tweaking this process, without breaking anything else, would be huge to extend our lifespan with some good quality years.
Reducing immune system load is fairly straightforward, low dose antibiotics is one approach that significantly reduces the effort put forth by the immune system.
However, it does not seem to make a significant difference in lifespans.
Some types of cancer are directly caused by infectious diseases. The HPV vaccine has greatly reduced cancer rates.
Moral of this story, figure out how to tell all the anti-vaccination people they are wrong in some way they will believe. (the first is easy, the latter is impossible in my experience)
