Immune Function and Stress

Immune System

• The immune system is responsible for maintaining homeostasis by recognizing harmful from non-harmful organisms and producing an appropriate response.
• Immunity is the ability of the body to fight infection and/or foreign invaders by producing antibodies (lymphocytes) or killing infected cells (natural killer cells).

Foreign Invaders

• Pathogens: Viruses, bacteria, or other living things that cause disease/immune response.
• Antigens: Toxins that pathogens produce that cause harm to an organism.

Immune System Components

• Blood: White Blood Cells (Lymphocytes) in particular.
• Lymph nodes: Site where immune cells interact and respond to pathogens.
• Thymus Gland: Produces T Lymphocytes.
• Bone Marrow: Produces B Lymphocytes.

Lines of Defense

• First Line of Defense: The Skin
  • Provides physical and chemical barriers.
  • Physical: hard to penetrate, made of indigestible keratin.
  • Chemical: tears, sweat.
• Second Line of Defense: Non-Specific Immune Response
  • Phagocytosis: done by Macrophages.
  • Macrophage: A phagocytic cell found in the liver, spleen, brain, and lungs.
  • Cytokines: cells that bind to other cells receptors to alert of pathogens around.
• Third Line of Defense: Specific Immune Response
  • Involves the creation of Antibodies.
  • Antibodies: Y-shaped protein molecule produced by B-Lymphocytes.
  • Function: Recognize antigens, bind to and deactivate them.

Immune Response

• Antigen infects cells.
• Macrophage ingests antigen and displays portion of it on its surface.
• Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active.
• Active Helper T-Cell activates Cytotoxic (killer) T-Cells and B-Cells.
• Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T-Cells.
• Active Cytotoxic T-Cells kill infected cells.
• At the same time, B-Cells divide into Plasma Cells and Memory B-Cells.
• Plasma cells produce antibodies that deactivate pathogen.
• Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

Allergies

• Allergy: An exaggerated response by the immune system to an allergen.
• Allergen: A normally harmless substance that causes an allergic reaction.
• Types of Allergic reactions:
  • Immediate: occurs within seconds and normally lasts for about 30 minutes.
  • Delayed: takes longer to react and can last for a much longer time.

Immune System and Stress

• Noradrenaline:
  • Innervates immune organs (lymph node, thymus, spleen, bone marrow).
  • Releases NE in close proximity to immune cells.
  • Leukocytes express a and b adrenergic receptors.
• Cortisol:
  • Inhibits lymphocyte proliferation.
  • Inhibits production of proinflammatory cytokines.
  • Shifts from Th1 to Th2 cell.

Individual Differences and the Immune System

• Age
• Disease Status
• Gender
• Personality
• Emotions
• Coping strategies

Prenatal Exposure to Stress and Immune Function

• Diminished cytokine response of leukocytes in rhesus monkeys.
• Altered lymphocyte count in male mice and adrenal hypertrophy was observed in female mice.

Immune Function and Stress

• Interaction of all the systems: Psychoneuroimmunology.
• Investigations of the bidirectional linkages between the CNS, the endocrine system, and the immune system, and the clinical implications of these linkages.

Studies

• Stress and effects on the aging immune system:
  • Stress mimics, intensifies, accelerates, and changes the functionality of cells.
  • Decrease telomere function and length.
• Intensified effects of aging on the immune system:
  • Age and chronic stress interact to predict responses to influenza vaccine.
  • Caregivers and well-matched controls found main effect of stress.
• Accelerated effects of aging on the immune system:
  • Stress may accelerate the effects of aging on inflammation.
  • Average caregiver experienced a 4-time increase in IL-6.
  • Among those caregivers, participants who were older than 75 had levels of IL-6 that made them at risk for disease.
  • Average non-caregiver participant would not reach this until the age of 90.

Possible Problems Related to Immune Dysfunction

• HIV/AIDS
• Cancer
• Cold
• Flu
• Herpes
• Recovery injury (wound healing)
• Infection

Cancer and Stress

• Chronic stress may disregulate DNA repair and regulation of cell growth, processes that have been shown to be major factors in tumor formation.
• Suppressing effect of chronic stress on the immune system also impacts the recovery period after surgery.

Growth, Spread, and Recovery

• Chronic stress seems to promote tumor growth and angiogenesis.
• More support for the strong interaction between chronic stress and cancer growth than between chronic stress and cancer development in humans.### Immune System and Wound Repair
• Neuroendocrine and immune function are relevant to wound repair.
• The immune system plays a key role in the early wound repair process.
• If the immune system is less efficient, it leads to slower healing.

Study: Emotional Disclosure Intervention

• Participants who wrote about traumatic events had significantly smaller wounds 14 and 21 days after the biopsy compared to those who wrote about time management.
• People with a therapeutic way to deal with stress give their immune system a boost, leading to faster healing.

Study: Stress, Cortisol Levels, and Wound Healing

• Low levels of cytokines at the site of the wound were found in participants with high levels of cortisol (= stress).
• The slower healing group showed higher stress levels, lower optimism, and higher cortisol compared to the faster healing group.

Immune System Overview

• Immunity: the ability of the body to fight infection and/or foreign invaders by producing antibodies (lymphocytes) or killing infected cells (natural killer cells).
• Immune System: the system in the body responsible for maintaining homeostasis by recognizing harmful from non-harmful organisms and producing an appropriate response.

Components of the Immune System

• Pathogens: Viruses, bacteria, or other living things that cause disease/immune response.
• Antigens: Toxins that pathogens produce, which cause harm to an organism.
• B cells create antibodies, and T cells recognize the antigens for B cells to recognize them.
• Natural killer cells: lymphocytes with no specific memory (i.e., killing machines).

Defense Mechanisms

• First line of defense: The skin provides physical and chemical barriers.
• Second line of defense: Non-specific immune response, including phagocytosis and the role of macrophages.

Types of Immunity

• Active Immunity: immunity where the body actively produces antibodies to fight infection, such as through vaccination.
• Passive Immunity: immunity where antibodies are given to a person from the blood of another person or animal, which only lasts for a short period.

Autoimmune Disease and Allergies

• Autoimmune disease: diseases where the immune system begins to attack itself, such as Rheumatoid Arthritis, Lupus, and Multiple Sclerosis.
• Allergy: an exaggerated response by the immune system to an allergen, which can cause an allergic reaction.

Interaction of Systems

• Psychoneuroimmunology: the bidirectional linkages between the CNS, the endocrine system, and the immune system, and the clinical implications of these linkages.

Noradrenaline and Cortisol

• Noradrenaline (NE) and epinephrine (E) can influence leukocyte activity and alter lymphocyte function.
• Cortisol has the effect of inhibiting lymphocyte proliferation and production of pro-inflammatory cytokines, and can shift from Th1 to Th2 cell responses.

Immune Response to Stress

• Exposure to acute stressors leads to the redistribution of immune cells and an increase in innate, non-specific immunity.
• Exposure to short-term stressors alters specific immunity, while exposure to chronic stressors decreases both Th1 cellular and Th2 humoral immune responses.

Individual Differences and the Immune System

• Age, disease status, gender, personality, emotions, and coping strategies can influence the immune system's response to stress.

Prenatal Exposure to Stress and Immune Function

• Prenatal exposure to stress can lead to diminished cytokine responses and altered lymphocyte counts in offspring.