iMMUNE FUNCTION AND STRESS

IMMUNE FUNCTION AND STRESS

Presenters: Dr. Syd Miller, Joelle Soucy, Suzanne Purcell, Kaitlyn Livingstone
Overview of Topics:

  • What is the immune system?

  • Immune response to stress

  • Stress and effects on the aging immune system

  • Cancer and Stress

  • Common Cold and Stress

  • Wound healing and Stress

WHAT IS THE IMMUNE SYSTEM?

  • Immunity: The ability of the body to fight infection and/or foreign invaders by producing antibodies or attacking infected cells.

  • Immune System: A collection of organs and cells responsible for maintaining homeostasis in the body by recognizing harmful organisms and producing an appropriate immune response.

FOREIGN INVADERS

  • Pathogens: Viruses, bacteria, or other organisms that cause disease or trigger an immune response.

  • Antigens: Toxic substances produced by pathogens that can cause harm to organisms.

COMPONENTS OF THE IMMUNE SYSTEM

  • Blood: White Blood Cells play a crucial role in immune response.

  • Lymphatic System: Includes organs such as:

    • Thymus: Produces T Lymphocytes; plays a role in cellular immunity.

    • Bone Marrow: Produces B Lymphocytes; essential for humoral immunity.

    • Spleen and Lymph Nodes: Act as filtration points for pathogens and sites for immune cell activation.

IMMUNE SYSTEM DEFENSE MECHANISMS

First Line of Defense (Physical and Chemical Barriers)

  • The Skin:

    • Physical Barrier: Hard to penetrate due to being made of indigestible keratin.

    • Chemical Barrier: Includes secretions like tears and sweat, which provide antimicrobial properties.

Second Line of Defense – Nonspecific Immune Response

  • Defenses are activated regardless of the type of invader:

    • Phagocytosis: Carried out by macrophages which engulf pathogens.

    • Natural Killer Cells: Attack infected or cancerous cells.

    • Inflammation: Triggered by histamines released from leukocytes to promote localized healing.

    • Fever: Response to infection; elevated body temperature denatures pathogen proteins.

    • Macrophages: Travel throughout the body, ingesting pathogens, and presenting antigens to T-Cells.

Third Line of Defense – Specific Immune Response

  • Involves a targeted response to a specific pathogen/antigen:

    • Antibodies:

    • Y-shaped protein molecules comprising variable (recognizes antigens) and constant (same in each antibody) regions, made from heavy and light chains. Produced by B-Lymphocytes.

    • Function: Attach to antigens and deactivate them.

PROCESS OF IMMUNE RESPONSE

Pathway of Specific Immune Response

  1. Pathogen Ingestion: Pathogens are eaten by macrophages.

  2. Antigen Presentation: Macrophages display portions of the pathogen on their surfaces.

  3. Helper T-cell Activation: Helper T-cells recognize this presented antigen and get activated.

  4. Activation of Cytotoxic T-Cells: They kill infected cells and activate B-cells to produce antibodies.

  5. Memory T and B cells: Remain in the body to provide a faster response upon future encounters with the same antigen.

  6. Suppressor T-cells: Stop the immune response once the invaders have been eliminated.

IMMUNE RESPONSE DYNAMICS

Primary vs. Secondary Immune Response

  • Primary Immune Response:

    • Initial response to an invader.

    • No measurable immune response for the first few days, followed by antibody production peaking in approximately 10-15 days.

  • Secondary Immune Response:

    • Occurs upon subsequent exposure to the same pathogen.

    • Rapid antibody production significantly increases in speed and amount.

TYPES OF IMMUNITY

Active vs. Passive Immunity

  • Active Immunity:

    • Body actively produces antibodies (e.g., during an infection, vaccination).

  • Passive Immunity:

    • Antibodies are transferred from another source (e.g., maternal antibodies in breastfeeding).

    • Short-lived immunity.

AUTOIMMUNE DISEASES

  • Diseases where the immune system attacks the body's own cells.

    • Examples:

    • Rheumatoid Arthritis: Affects joints.

    • Lupus: Affects blood and organs.

    • Multiple Sclerosis: Affects the nervous system.

ALLERGIES

  • Allergy: Exaggerated immune response to a normally harmless allergen (e.g., dust, pollen, certain foods).

    • Types of Allergic Reactions:

    • Immediate: Occurs within seconds, lasts about 30 minutes.

    • Delayed: Takes longer to react and lasts for an extended period.

  • Mechanism of Action:

    • Involves the rapid release of histamines, which cause symptoms such as tissue swelling, fluid release, and muscle spasms.

    • Anaphylaxis: Severe, life-threatening allergic reaction.

  • Treatments:

    • Avoidance of allergens, epinephrine (for anaphylactic shock), and antihistamines (e.g., Benadryl).

INTERACTIONS WITH STRESS

Psychoneuroimmunology

  • Studies the relationship between the central nervous system (CNS), endocrine system, and immune system, and their clinical implications.

Effects of Stress on Immune Function

Acute Stressors

  • Activates hypothalamic-pituitary-adrenal (HPA) axis, leading to the release of glucocorticoids and catecholamines.

  • Results in a redistribution of immune cells, increasing non-specific immunity (e.g., NK cells) but decreasing specific immunity.

Chronic Stressors

  • Long-term exposure leads to detrimental effects on both innate (non-specific) and adaptive (specific) immunity.

  • Increased inflammatory activity while decreasing overall immune responses.

Age and Stress Impact

  • Stress significantly affects immune function:

    • Aging enhances the effects of stress on the immune system, leading to increased vulnerability.

    • Chronic stress can activate and amplify the inflammatory response at an accelerated pace.

STRESS AND CANCER

  • Inconsistency in human studies regarding stress as a risk factor for cancer.

    • Animal models suggest chronic stress may disrupt DNA repair and trigger tumor formation. - Stress can affect recovery after treatment due to impaired immune function.

STRESS AND COMMON COLD

  • Studies show chronic stress correlates with increased susceptibility to colds, with regarding types and durations of stressors contributing to the likelihood of cold infection. - Individuals exposed to chronic interpersonal and work-related stress are more susceptible.

WOUND HEALING AND STRESS

  • Studies on patients (e.g., surgery recovery) indicate that high levels of stress lead to slower wound healing. - Emotional disclosure, through writing about traumatic events, significantly improved wound healing compared to control groups focused on planning.

  • Healing correlated with levels of stress, shown through cytokine responses.