In this video I briefly describe the immune system and the cells involved in surveillance and protection from invaders, pathogens, and other threats. Next I discuss the relationship between stress and decreased immune function, which is related to elevated levels of glucocorticoids. This can also be seen in treatment of autoimmune disorders that uses glucocorticoids to suppress immune function. Lastly I discuss how chronic stress is associated with accelerated aging and the shortening of telomeres on the ends of chromosomes.
Cohen, S. et al (1998) Types of Stressors that Increase Susceptibility to the Common Cold in Adults: http://www.psy.cmu.edu/~scohen/types%…
Epel, E.S. et al (2004) Accelerated telomere shortening in response to life stress: https://static1.squarespace.com/stati…
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Video Transcript
Hi, I’m Michael Corayer and this is Psych Exam Review. In this video we’re going to look at some details of the immune system in order to better understand how stress can influence our health. So the immune system refers to the body’s natural defense against things like intruders, pathogens, or injury and we can think of it as having two main functions. There’s a surveillance function, where it has to look out for invading cells or potentially dangerous cells, or look out for sites of injury. And then a protection system where it breaks down or destroys invading cells or helps us to recover from injury.
So it does this through a number of different types of cells and one of these types of cells are lymphocytes. These are white blood cells, and here’s a picture of a lymphocyte here, and these lymphocytes come in two main types; there are T cells and B cells. T cells refer to lymphocytes that are originating from the thymus and B cells refer to lymphocytes that originate from the bone marrow. What these lymphocytes do is they’re able to identify invading cells and then they produce antibodies that can help us to fight off these invaders.
And lymphocytes are aided in this task of fighting off invading cells by a couple other cell types including macrophages. Here’s a macrophage here and that’s this large cell here with these tendrils coming off of it. This is the macrophage and macrophage comes from the Greek for “big eater” and what macrophages are able to do is they can actually consume invading cells or damaged cells in the body and then break them down and eliminate them. So that’s macrophages and then we also have what are called natural killer cells. And here this orange yellow cell here is the natural killer cell and these are cells that can directly attack and destroy invaders.
Ok, so what does all this have to do with the stress response? Well what we find is that part of the stress response involves the release of these steroid hormones called glucocorticoids and these mobilize energy and increase glucose in the bloodstream. But the release of glucocorticoids and the glucocorticoids circulating in the bloodstream can interfere with the immune systems functioning. One way we can see this is a study by Sheldon Cohen and colleagues in 1998 and what Cohen and colleagues did was they had participants rate their recent levels of stress and then they gave these participants nasal drops that had a cold virus and what they then did is looked at who got sick from the virus; who actually developed an illness from being exposed to this cold virus? And what they found was that it was the people who had reported higher levels of stress. So if you were under a lot of stress and then you were exposed to this virus, you were more likely to get sick then if you hadn’t had a high level of stress. The people with lower stress ratings were less likely to get sick and this indicates that the stress is interfering with the immune system’s ability to fight off this virus.
And we can also see that glucocorticoids are associated with degeneration of neurons in the hippocampus and they’re associated with greater fat storage and in particular storage of fat in the abdomen. This is something we’ll come back to in a future video. Another way we can see how glucocorticoids relate to the immune system is with autoimmune disorders. So an autoimmune disorder is a disorder where the immune system incorrectly begins attacking healthy cells. It’s misidentifying these as invaders or dangerous cells and so it starts attacking them and one example of this we saw in the previous unit was multiple sclerosis. In multiple sclerosis the immune system incorrectly begins attacking the myelin on neurons and breaking it down. But we also have other autoimmune disorders where the immune system attacks healthy cells in the body and these include rheumatoid arthritis as well as psoriasis.
The way that these types of autoimmune disorders can be treated, one technique for treating them, is to give patients high doses of glucocorticoids. Because this is going to suppress the immune system’s functioning and by suppressing the immune systems functioning it’s less able to attack the body’s own healthy cells. And the downside is it’s less able to fight off other invaders or infections or potentially dangerous cells, but this is the trade-off that has to be made. So we can see here the use of glucocorticoids is suppressing immune function and that in this case reduces the symptoms of these autoimmune disorders. Glucocorticoids can also be used to reduce the immune system’s response to organ transplants. So the body tries to reject these invading cells of the transplanted organ and one way to reduce that rejection is to use glucocorticoids.
And finally we can see stress influences the telomeres on the ends of chromosomes. So here’s a picture of a telomere, or a representation of telomeres on a chromosome. So this is a chromosome here and at the ends of chromosomes we have these things called telomeres and these are sequences of nucleotides and these are involved in the process of cell division. Over time the telomeres shorten with aging and so each time the cell is dividing this is gradually reducing the size of the telomere until eventually the telomeres become too short to function and the cell can no longer divide and this is called senescence. What we see is that stress is associated with acceleration of this shortening of telomeres. So telomeres naturally shorten over time, the more the cells divide, so they’re associated with aging but this process of shortening the telomeres is accelerated by chronic stress. This is part of the reason why people who are under lots of stress appear to age more quickly is they actually are aging. Their telomeres are aging more quickly than people who are under less stress and this was demonstrated in a study by Elissa Epel and colleagues in 2004. What they found was that mothers who were taking care of chronically ill children, so these mothers were under very chronic stress for a long period of time, and they found that these mothers had shorter telomeres than mothers who were caring for healthy children. This again suggested this relationship between chronic stress and the shortening of telomeres at a more accelerated rate. Ok, I hope you found this helpful, if so, please like the video and subscribe to the channel for more. Thanks for watching!
