immune_system

Immune System Overview

• Instructor: Ms. Melody S. Dalag

Body Defenses

General Overview

• Viruses and bacteria are ubiquitous; some seek to invade the body.

• The body uses various mechanisms to defend itself against these pathogens.

• Key principle: WORK TOGETHER to ensure effective defense.

Defense Against Disease

• If external barriers are breached, the body employs different responses:

  • Innate Immune Response: Quick, non-specific defense mechanisms.

  • Adaptive Immune Response: Specific and long-lasting immunity developed through:

    • Cell-mediated immunity

    • Humoral immunity

• Key components of defense:

  • Nonspecific External Barriers:

    • Skin

    • Mucous membranes

  • Innate Immune Response:

    • Phagocytic cells

    • Natural killer cells

    • Inflammatory response

    • Fever

First Line of Defense

• The non-specific defenses include:

  • Intact skin: Physical barrier against pathogens.

  • Mucus and Cilia: Trap and expel invaders from respiratory tract.

  • Phagocytes: Target and destroy pathogens.

Role of Phagocytes

• Phagocytes are types of white blood cells (e.g., macrophages, neutrophils).

• Function: Seek and destroy foreign invaders and damaged body cells.

• Phagocytes activation: Stimulated by inflammatory signals from damaged cells.

Role of Inflammation

• Inflammation response initiated by mast cells releasing histamine:

  • Histamine helps fluids accumulate around injuries, diluting toxins and causing swelling.

  • Elevated tissue temperature may help eliminate temperature-sensitive microbes.

Role of Fever

• Fever is a defensive mechanism against infections:

  • Can destroy various pathogens.

  • Enhances viral infection resistance by boosting interferon production.

  • Caution: Extremely high fevers can be dangerous; moderate fevers are often allowed without treatment.

Specific Defenses

• Specific defenses provide immunity to certain diseases:

  • The immune system creates a chemical "memory" of pathogens, facilitating rapid responses to repeat infections to minimize symptoms.

Major Players in the Immune System

• Key components of the immune response include:

  • Macrophages

  • T cells: Helper T cells, Cytotoxic T cells, Memory T cells

  • B cells: Plasma cells, Memory B cells

  • Antibodies

Antibodies

• Composed of protein chains; various configurations create unique antibodies.

Helper T Cells

• Recognize antigens through specific receptors and stimulate B-cell division via cytokines.

• Critical for signaling an immune response:

  • Disability (e.g., in AIDS) leads to impaired immune response.

B Cells

• Function primarily to produce antibodies:

  • B cells with matching antibodies undergo rapid division and differentiation into:

    • Plasma cells: Produce antibodies quickly.

    • Memory B-cells: Maintain memory of the invader for future encounters.

Role of Antibodies

• Antibodies bind to specific antigens in the bloodstream:

  • May disable pathogens or encourage agglutination.

  • Tag pathogens for recognition and destruction by other white blood cells.

“Killer” T Cells

• T cells also proliferate and differentiate:

  • Some develop into cytotoxic or “killer” T cells which seek out and destroy any recognized antigens and microbes marked by antibodies.

  • Capable of targeting cancer cells.

Supporting the Immune System

• Medical interventions to bolster immune defenses include:

  • Antibiotics: Target bacterial infections (not the same as antibodies).

  • Vaccines: Train immune system for future encounters with pathogens.

How Vaccines Work

• Created using killed microbes or protein fragments:

  • Recognized as antigens, inducing a mild immune response.

  • Leads to production of memory T-cells and B-cells for future protection against the illness.

Autoimmune Disorders

• Occur when the immune system incorrectly identifies body proteins as foreign:

  • Examples: Multiple sclerosis, lupus, rheumatoid arthritis.

  • No cure available; treatment focuses on managing symptoms and slowing progression.