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Stress and Immunity A Case Study in Evolution and Immunology

Stress and Immunity A Case Study in Evolution and Immunology. Jory P. Weintraub, Ph.D. National Evolutionary Synthesis Center (NESCent) Durham, NC. Stress and Immunity: Outline. Introduction – What is Immunology? What is Evolution? How are they related?

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Stress and Immunity A Case Study in Evolution and Immunology

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  1. Stress and ImmunityA Case Study in Evolution and Immunology Jory P. Weintraub, Ph.D. National Evolutionary Synthesis Center (NESCent) Durham, NC

  2. Stress and Immunity: Outline • Introduction – What is Immunology? What is Evolution? How are they related? • The Evolution of a Discipline: PsychoNeuroImmunology (PNI) and the Stress Response • Case Study – Stress, Immunity and Evolution • Links, References and Readings Weintraub, 2007

  3. What is Immunology? • The study of the mechanisms used by the body to protect against environmental agents that are foreign to the body (“challenges”). • The study of how the body defends itself against infectious agents and pathogens. Weintraub, 2007

  4. Clearance of Infection Immune System Challenge/Antigen (e.g. bacteria) X Self Antigen (e.g. DNA) Clearance of Infection No Response (Tolerance) Function of the Immune System Non-self (foreign) Self Weintraub, 2007

  5. The Role of the Immune System • Distinction between foreign and self • Recognition of challenge • Elimination of challenge Weintraub, 2007

  6. What is Evolution? • Evolution is a unifying principle in biology which describes descent with modification and change in inherited traits in a population over time. • Evolution occurs when inheritable differences in organisms become more or less rare over time. • This can happen through natural selection (a non-random process whereby advantageous traits allow for survival and are passed on genetically to offspring), or it can occur through the random process of genetic drift. Weintraub, 2007

  7. What are some ways that immunity and evolution might be related to each other?Can anyone think of examples? Weintraub, 2007

  8. Stress and Immunity: Outline • Introduction – What is Immunology? What is Evolution? How are they related? • The Evolution of a Discipline: PsychoNeuroImmunology (PNI) and the Stress Response • Case Study – Stress, Immunity and Evolution • Links, References and Readings Weintraub, 2007

  9. PsychoNeuroImmunology (PNI) • In 1975 Ader and Cohen published a paper demonstrating that the immune system could be activated or suppressed as a conditioned response to a behavioral or psychological stimulus. • In other words, certain behaviors, situations or psychological stimuli can turn the immune system on or off. • This observation established a link between behavior, the nervous system and the immune system… Psychoneuroimmunology (PNI) is born. Weintraub, 2007

  10. The Nervous System (Neurobiology) PNI Behavior (Psychology) The Immune System (Immunology) PsychoNeuroImmunology (PNI) The link between the Nervous System, the Immune System and Behavior Weintraub, 2007

  11. PsychoNeuroImmunology (PNI) A classic example of this brain-behavior-immunity connection is the stress response. Among its other effects, physical or psychological stress can alter immune function. Weintraub, 2007

  12. Animal studies show that stress impairs immune function (Visintainer et al., Science, 1982) • Rats are connected to electrodes. The shock they receive is either inescapable (high stress) or escapable when the rat presses a lever (low stress). Controls receive no shock. • High stress inhibits rats’ immune response (as measured by ability to reject tumors which have been surgically implanted). Weintraub, 2007

  13. Similar results are seen in humans • Medical students were asked to estimate their level of psychological stress on a scale of 0-12 (“12” being “highest stress level”) • General health status is used as a measurement of immune function (“developing a cold” indicates impaired or suppressed immune function) Weintraub, 2007

  14. How might this have evolved?Why might this have evolved?Let’s look at a case study… Weintraub, 2007

  15. Stress and Immunity: Outline • Introduction – What is Immunology? What is Evolution? How are they related? • The Evolution of a Discipline: PsychoNeuroImmunology (PNI) and the Stress Response • Case Study – Stress, Immunity and Evolution • Links, References and Readings Weintraub, 2007

  16. Case Study: Stress and Immunity The Facts: • Emotional stress is known to trigger the nervous system to release a chemical called cortisol into the blood. • Cortisol is a steroid. • Steroids can prevent production of cytokines. • Cytokines are proteins that activate or “turn on” cells of the immune system. Weintraub, 2007

  17. Case Study: Stress and Immunity The Case The students enrolled in a biology class are randomly divided up into two groups. GROUP 1 will be provided with old exams, practice tests and annotated lecture notes prior to the midterm. They will be allowed to bring these materials to class and use them during the untimed exam. GROUP 2 will be given none of these materials in advance, and the exam will be “closed book, no notes”. The exam will be timed, and their scores will be published on the front page of the school newspaper. The instructor has a terrible cold, and as she is informing the class of these two groups she is also coughing and sneezing all over them. Weintraub, 2007

  18. Case Study: Stress and Immunity Question #1 How would you predict each of the two groups will react to their exposure to the instructor’s cold? Explain your answer… Weintraub, 2007

  19. Case Study: Stress and Immunity Question #2 What is happening at a cellular and/or molecular level to cause this? Weintraub, 2007

  20. Case Study: Stress and Immunity Question #3 (The “Big Question”) Speculate why this mechanism has evolved in humans over time. How might it be advantageous? If you think it’s not advantageous, why does it occur? Weintraub, 2007

  21. Stress and Immunity: Outline • Introduction – What is Immunology? What is Evolution? How are they related? • The Evolution of a Discipline: PsychoNeuroImmunology (PNI) and the Stress Response • Case Study – Stress, Immunity and Evolution • Links, References and Readings Weintraub, 2007

  22. Links, References, Readings • The original Ader and Cohen article from 1975: http://www.psychosomaticmedicine.org/cgi/reprint/37/4/333 • Wikipedia entry on Psychoneuroimmunology:http://en.wikipedia.org/wiki/Psychoneuroimmunology • “Why Study the Evolution of Immunity?” (an article in the journal Nature Immunology): http://www.nature.com/ni/journal/v8/n6/full/ni0607-547.html Weintraub, 2007

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