Basic Principles of Immunity
Define psychological stress as we have learned it in terms of PNI
Stress occurs when our
perceived demands of the
world exceed what we believe are
our capabilities.
List some of the classic tests or paradigms used in PNI to test the immune system.
Snot test to measure the level of cold in a body
Stress and isolation with rats
Measuring levels of cytokine activity
Asking participants how stressed they are, family trauma (if their parents owned their own home)
What does the HPA axis stand for?
Hypothalamus-Pituitary-Adrenal axis. The HPA axis is a central stress response system in the body.
why is sleep altered during sickness?
When a person gets sick, the immune system produces pro-inflammatory cytokines in order to fight off the infection. Some of these cytokines promote sleep, Nonrapid eye movement in particular. This is why someone may sleep for days but continue to be tired because they never reach REM sleep. The body is also trying to conserve energy when sick to fight off the infection. Therefore the body increases rest so that it can focus more on fighting off the infection (producing anti-bodies). Fevers are produced during sickness to help fight off infection but fevers tend to make people more tired. The immune response can lead to many awakenings during sleep and less time in REM. This is due to pain, fever, discomfort, and inflammatory signals affecting how the brain controls sleep. This is why when sick you can sleep for hours on end but still feel tired. Circadian rhythm during sickness can shift which increases sleepiness at different times of the day.
what are some examples of sickness behavior?
Sickness behavior is when your body reallocates its motivations to heal your body in a similar fashion as symptoms of depression but for a shorter period of time and are reversible.
A shift in your Motivational state
Not going to class, not wanting to get out of bed, not wanting to explore (mouse example), fatigue, social withdrawal, lack of appetite, irritability (mood), malaise, down
Describe the 4 principles of the innate immune system
- response time
-specificity
-response to repeat infection
-major components
Response time: hours
Specificity: limited and fixed
Response to repeat infection: identical to the primary response
Major Components: barriers, phagocytes, pattern recognition molecules
what does “reverse engineering” mean in PNI
Reverse engineering means taking a complicated system such as the HPA axis and analyzing it in a deconstructed fashion to make more sense of the interconnected system. By working backward from observable effects, researchers aim to identify the underlying mechanisms or pathways responsible for those effects.
why is the statement “stress is bad for you” not correct?
Stress is when our perceived demands of the world exceed what we believe are our capabilities
The statement “stress is bad for you” is wrong because stress can be good for you to get out of situations that may be life-threatening. For example, if you become stressed in a dark alley, this can be beneficial because your body will react and get you out of the unsafe situation that you may be in. “fight or flight” Chronic stress can be harmful for your overall health but acute stress can motivate you to get out of dangerous situations and help you adapt to new challenges. Stress also builds self-resilience so you can cope better in future stressful situations. Acute stress produces cortisol and adrenaline in the body which prepare you for dangerous or difficult experiences.
how does sleep change with immunizations?
Immunizations often lead to an increase in NREM sleep and a reduction in REM sleep due to the immune response. These changes are driven by cytokines released during inflammation, which also help support antibody production and immune memory. Ensuring adequate sleep before and after vaccination is important for maximizing vaccine efficacy and minimizing the impact of side effects on sleep quality
how do cytokines move from the body to the brain, impacting mood and behavior?
Cytokines influence the brain through direct and indirect mechanisms, including crossing the BBB, signaling via the vagus nerve, activating endothelial cells, and recruiting immune cells. Once in the central nervous system, cytokines induce neuroinflammation, change neurotransmitter function, and dysregulate the HPA axis, leading to changes in mood and behavior. This explains how immune activation contributes to conditions like depression, anxiety, and sickness behavior
Describe the 4 principles of the adaptive immune system
- response time
-specificity
-response to repeat infection
-major components
response time: days
specificity: highly diverse; improves during the course of immune response
response to repeat infection: more rapid than the primary response
major components: lymphocytes; antigen-specific receptors; antibodies
what are the 4 ways to identify psychobiological mechanisms?
research linking psychosocial factors to disease outcome
research linking psychosocial factors to biological intermediaries
research identifying the biological chain of causality
research connecting discoveries across these 3 domains
which stressor does not activate the HPA axis? Options include social evaluative threat, unpredictability, aversive stimuli, and low perceived control.
Adverse stimuli
what is the connection between cytokines, sleep, and depression?
Cytokines influence both sleep and depression by modulating inflammatory responses, neurotransmitter systems, and neuroendocrine function. Sleep disturbances caused by cytokine activity increase depressive symptoms, while depression and poor sleep further increase inflammation, creating a negative and detrimental cycle.
explain the connection between sickness behavior and psychological symptoms of depression (somatic and vegetative states)
Pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, are elevated in sickness behavior. These same cytokines are implicated in depression, particularly in patients with chronic inflammatory conditions. Cytokines affect the brain via the vagus nerve, direct transport across the BBB, or by stimulating the production of secondary messengers like prostaglandins.
Sickness behavior and depression involve heightened HPA axis activity, leading to elevated cortisol levels. Chronic cortisol exposure contributes to mood dysregulation, energy deficits, and cognitive impairment, mirroring depressive symptoms
describe what the graph of these 4 psychological stress responses will look like: repeated hits, lack of adaptation, prolonged response, and inadequate response. use physiological response on the y-axis and time on the x-axis.
repeated hits is a graph that shoots up and down in physiological response versus time
lack of adaptation is a graph that shows the same pattern as the repeated hits graph but it is clear that the immune system is not responding as it should be and adapting because there is also a red line on the graph which shows the normal adaptation response in comparison to the lack of adaptation response
a prolonged response is a graph that goes up, then plateaus and remains plateaued rather than coming back down
inadequate response is a graph that shows a very small response and hardly goes up or down on the y-axis.
what is the importance of measuring eosinophils and mast cells in children with asthma, not natural killer cells?
Measuring eosinophils and mast cells is directly related to asthma due to their central role in airway inflammation and allergic responses. Natural killer cells are not directly relevant to asthma's inflammatory mechanisms, making them less important for asthma evaluation in children
what are the 2 examples of negative feedback loops we learned about in this course?
When we are sick, which of the following is not changed about our sleep?
- Fever makes us feel malaise and discomfort, and this reduces total sleep time
-Shivering is enabled when REM sleep is suppressed
-We don't lose as much heat during our sleep when our non-REM is fragmented
-Our non-REM sleep is increased because it helps us conserves energy
Fever makes us feel malaise and discomfort, and this reduces total sleep time
what is tryptophan and how is it involved in sickness behavior and depression?
Tryptophan is an amino acid needed for normal growth in infants and for the production and maintenance of the body's proteins, muscles, enzymes, and neurotransmitters. It is also a protein that we eat which turns into serotonin. It influences mood and behavior through its role in serotonin and kynurenine metabolism. Inflammatory processes divert tryptophan metabolism toward the kynurenine pathway, reducing serotonin availability.
define the difference between macrophages and monocytes and the importance/significance of both for the immune system.
monocytes are white blood cells that circulate the bloodstream and are a key player in the innate immune system. Macrophages are monocytes that reside within tissues.
Monocytes are important for the immune system because they quickly respond to infection and release signaling molecules to help fight infection.
The importance of macrophages is to help fight infection by releasing growth hormones and getting rid of dead or damaged cells. Macrophages conform to the specific tissues needs.
which of these options directly impacts how stress affects immune responses?
A. The duration of the stressor.
B. The availability of nutrients.
C. The time of day the stress occurs.
D. The type of coping mechanisms used.
Duration of stressor because this determines if stress is chronic or acute which both have different effects on the immune system. Acute stress puts the body into fight or flight mode, whereas chronic stress suppresses the immune system affecting future responses to stressors and recovery.
what is the definition of a negative feedback loop in terms of PNI?
A negative feedback loop in PNI is when a physiological response to a stimulus reduces the original stimuli, keeping the body in homeostasis when it should be reacting.
explain the connection between sleep after an IL-1 injection
An IL-1 injection induces significant changes in sleep, characterized by increased NREM sleep, reduced REM sleep, and sometimes fragmented sleep. These effects prove that IL-1 acts as a mediator between the immune system and sleep regulation, showing how the body adapts its sleep patterns during immune activation to promote recovery and resilience
what are the implications of depression for medically ill people/ explain how the links between depression and sickness behavior explain the high rates of depression in medically ill people.
Diseases like cancer, cardiovascular disorders, autoimmune diseases, and chronic infections are associated with prolonged inflammation, which mirrors the processes underlying sickness behavior and depression. The high rates of depression in medically ill individuals are explained by shared biological mechanisms between sickness behavior and depression, driven by chronic inflammation, neurotransmitter dysregulation, and neuroinflammation.