L3: Stress & the Immune System

Question 1

what are immune cells?

Answer 1

white blood cells aka leukocytes which are produced by stem cells in the bone marrox
lots of types including lymphocytes (t cells, b cells) and monocytes

Question 2

what does the bone marrow do?

Answer 2

immune cells originate from it in 2 types:
- lymphoid lineage (lymphocytes)
- myeloid lineage (macrophage, mast cell, dendritic cell, granulocytes / polymorphonuclear leukocytes)

Question 3

use a military analogy to explain how the immune system works

Answer 3

• skin & mucosa are front lines aka first line of defense against pathogens
• lymph nodes are headquarters where immune cells like lymphocytes are activated & coordinated to respond to an infeciton after beinga lerted by signals from the front lines

Question 4

how does the immune response work?

Answer 4

1. initial infection: an infection when a pathogen breaches the skin & mucose (the IS’s first barriers), its intercepted by sentinel cells (like macrophages, dendritic cells)
2. lymphatic system: pathogens are carried through the lympathic system to the lymph nodes, where lymphocytes (T and B cells) recognise the invader
3. effector cells: lymphocytes in the lymph nodes become armed effector cells & circulate in the blood to target & kill infected cells in the skin or mucosa

Question 5

what are the barriers of the immune system?

Answer 5

• skin: acts as physical barrier supported by endogenous flora & low pH
• mucosa: acts as physical barriers w mucus containing antimicrobial proteins

Question 6

what happens when frontline defenses are breached?

Answer 6

1. physical barriers & body temperature help prevent the spread
2. chemical defenses: like antimicrobial proteins (eg: lysozymes, complement proteins)
3. phagocytic response: phagocytic cells like neutrohpils & macrophages recognize pathogens through pattern recognition receptors & destroy them, initiate inflammation, and transport antigens to lymphoid organs

Question 7

what is the function of the phagocytic response?

Answer 7

• destruction of pathogens
• activation of the inflammatory response (cytokines are released, causing illness symptoms)
• transport of antigens to lymphoid organs for a broader immune response

Question 8

define activation (in IS context)

Answer 8

cellular changes to trigger immune responses

Question 9

define antigen

Answer 9

a molecule that initiates an immune response (triggers antibody production)

Question 10

define cytokines

Answer 10

signaling molecules in the immune system

Question 11

what is the role of lymph nodes?

Answer 11

they concentrate antigens and lymphocytes, increasing the likelihood of an antigen meeting its specific immune receptor

Question 12

what is the difference between immune cells, leukocytes, lymphocytes, and t cells

Answer 12

immune cells: broadest category, includes all cells that participate in immune response; sometimes used to refer to leukocytes
leukocytes: type of immune cell, aka white blood cells. includes lymphocytes, monocytes, neutrophils etc
lymphocytes: subtype of leukocyte that includes T cells, B cells, and NK cells
T cells: type of lymphocyte involved in the adaptive immune respnse

Question 13

what are the most important types of lymphocytes and their functions?

Answer 13

• cytotoxic T cells: kill virus-infected and cancer cells
• helper T cells: release cytokines to regulate immunity
• B cells: produce antibodies as part of humoral aka fluid immunity

Question 14

what is adaptive immunity?

Answer 14

• uses lymphocytes, which have specificty for certain pathogens
• slow initial response, but develops memory for faster responses in future encounters

Question 15

what is innate immunity?

Answer 15

• broad and fast, based on pattern recognition, but it does not improve w repeated exposures

Question 16

what are the lymphocyte development phases?

Answer 16

1. activation of naive lymphocytes
2. production of effector cells (T & B cells) to fight infections
3. some cells become memory cells, making future immune response faster & stronger

Question 17

what happens to the lymphocytes after infection?

Answer 17

• most effector cells (t & b cells) die after pathogen is eliminated
• memory cells survive, enabling a quicker and more vigorous response upon re infection

Question 18

what are the 3 functions of the Immune system?

Answer 18

1. protection against infectious disease
2. destruction against malignant transformations
3. promotion of tissue repair

Question 19

what are the unwanted side effects of the immune system?

Answer 19

1. discomfort and sickness
2. tissue damage
3. often disease is not caused by the pathogen, but by the immune system responses to it

Question 20

what kind of partners do we prefer (IS related)?

Answer 20

w different MHC type, which they can detect by smell

Question 21

how was conditioned taste aversion shown?

Answer 21

rats, after associating flavored liquid w sickness, develop an aversion to it
even when forced to consume the flavor again w/o the sickness inducing agent, they still react w illness

Question 22

how does conditioned immune suppression work?

Answer 22

Rats conditioned with an immune suppressant have suppressed immune responses even when exposed to antigens without the suppressant

Question 23

what is the relationship between depression & immunity?

Answer 23

depression can slow wound healing & is assocaited w elevated inflammation (cytokines)
inflammation can then trigger fatigue, low mood, and social withdrawal, contributing to depression

Question 24

what is the relaitonsihp between depression & inflammation?

Answer 24

Higher inflammation can predict future depression, but depression doesn’t predict future inflammation.
Anti-inflammatory drugs can have antidepressant effects, though more research is needed.

Question 25

what does the immune enhancement model show?

Answer 25

Short-term stress enhances the immune system, increasing immune activity, hormone release (like cortisol), and improved detection of pathogens, aiding in quick response to threats.

Question 26

what is the general relation between mental illness & immune related illnesses like rheumatoid arthritis?

Answer 26

individuals w immune related illnesses are at higher risk of mental health issues
everything is worse when u have both

Question 27

what is the relationship between stressors & immune dysregulation?

Answer 27

• chronic stressors impair immune function:
• increase susceptibility to infections
• influence disease severity
• reduce vaccine efficacy
• reactivate latent herpesviruses
• slow wound healing (due to high levels of corticosteroids)
• increased production of pro inflammatory cytokynes contributing to age related diseases
• accelerated progression of HIV
• very brief stressors (less than 2h) may enhance certain aspects of immune function (like cell trafficking)
• ability to “unwind” after stressful events is thought to influendce the burden stressors place on an individual

Question 28

how does the endocrine system interact w the immune system?

Answer 28

• theres bidirectional communication
• stress activates the hypothalamic pituitary adrenal HPA axis & sympathetic adrenal medullary SAM axis
• these release hormones (like cortisol) & alter immmune responses
• these hormones directly and indirectly affect immune cells & cytokine production

Question 29

how does the CNS interact w the immune system?

Answer 29

• cns influences immune functions via hormone receptors on immune cells
• lymphocytes can also produce hormones, changing immune responses

Question 30

Is stress bad for immune function?

how/why/can you illustrate your argument w 2 examples

Answer 30

• impaired immune response to vaccination (ppl w chronic stress respond less to influenza vaccine; stress also impairs hepatitis b and rubella vaccine)
• increases susceptibility to viral infections (ppl w rhinovirus who reported more stress had more cold symptoms; stress accelerate disease progression in HIV)
• reactivation of latent viruses (stress can reactivate genital herpes; stress associated with reactivation of varicella zoster virus)
• dysregulated immune reponse to virus (in mice, stress altered immune response to influenza; stressed humans w respiratory viruses had weaker also weaker immune response)