Overview of Immunity

Overview of Immunity

• Immunity is the body's ability to resist infection and disease.
• It involves a complex system of cells, tissues, and organs working together to identify and eliminate foreign invaders.
• Two main branches of the immune system: innate and adaptive.

Innate Immunity

• Provides a rapid, non-specific defense against a wide range of pathogens.
• The first line of defense against infection.
• Includes physical barriers (skin, mucous membranes) and cellular components (phagocytes, natural killer cells).
• Phagocytes engulf and destroy pathogens.
• Natural killer (NK) cells kill infected or cancerous cells.
• Inflammatory response: a localized reaction characterized by redness, swelling, heat, and pain.

Adaptive Immunity

• Provides a slower, more specific response tailored to specific pathogens.
• Develops immunological memory, allowing for faster and more effective responses to subsequent encounters with the same pathogen.
• Two main types of adaptive immune responses:
  • Cell-mediated immunity: involves T lymphocytes (T cells), which directly attack infected cells.
  • Humoral immunity: involves B lymphocytes (B cells), which produce antibodies that bind to and neutralize pathogens.

Components of Adaptive Immunity

• Lymphocytes: white blood cells responsible for adaptive immunity.
  • B cells differentiate into plasma cells, producing antibodies.
  • T cells: helper T cells activate B cells and cytotoxic T cells; killer T cells directly destroy infected cells.
• Antibodies: proteins produced by B cells that bind to specific antigens (molecules on the surface of pathogens).
• Antigens: molecules that trigger an immune response.
• Lymphocyte activation: a process where lymphocytes are activated by encountering antigens.
• Memory cells: long-lived lymphocytes that remember previous encounters with a specific pathogen, enabling a faster, stronger response upon re-exposure.

Types of Immunity

• Active immunity: acquired through exposure to a pathogen or vaccination.
• Passive immunity: acquired through the transfer of antibodies from another source, such as through breast milk or injection.

Immune System Disorders

• Immunodeficiency disorders: occur when the immune system is weakened or impaired, increasing susceptibility to infections.
• Autoimmune disorders: occur when the immune system mistakenly attacks the body's own tissues.
• Allergies: occur when the immune system overreacts to harmless substances.

Factors Affecting Immune Function

• Age: the immune system matures over time, affecting susceptibility in children and older adults.
• Nutrition: a balanced diet provides essential nutrients for optimal immune function.
• Stress: chronic stress can weaken the immune system.
• Lifestyle factors: smoking, alcohol consumption, and lack of exercise may compromise the immune system.
• Genetics: genetic predisposition influences immune response.

Vaccination

• Vaccination triggers an adaptive immune response without causing illness.
• It primes the immune system to efficiently recognize and eliminate a pathogen if encountered later.
• Vaccines typically introduce a weakened or inactive form of the pathogen or a piece of it.