Immunity

Innate and Adaptive Immunity

Innate Immunity
  • Basic resistance to disease that an individual is born with.
  • Rapid protection against microbes, activated immediately.
  • Operates before specific foreign challenges (antigens) present.
  • Response is uniform, irrespective of the antigen; there is no memory involved.
Adaptive Immunity
  • Protection develops more slowly (days) as it is acquired after exposure to specific antigens.
  • Resulting products are effective against specific antigens only.
  • Possesses memory capabilities that enhance responses to recurring antigens.
Key Terms
  • Self: Particles (proteins, etc.) made by one’s body; not targeted by the immune system.
  • Non-self: External particles (bacteria, viruses, etc.) and their proteins (antigens) that trigger immune responses.
Understanding Antigens
  • Antigens work as identification tags indicating potential threats.
  • Can be whole pathogens or proteins they express.
  • Some antigens are general and some are specific to particular pathogens.

Innate Immune System

  • Comprises immediate defenses against infection when a pathogen attacks.
  • First Line of Defense:
    • Physical Barriers: Skin, mucus membranes.
    • Chemical Defenses: Acidic skin surface, enzymes in sweat/tears.
    • Resident Flora: Normal bacteria prevents other infections.
Defense Mechanisms
  • Second Line of Defense:
    • Activation of immune cells and proteins.
    • Inflammatory response includes redness and swelling.
    • Fever response induces higher body temperature, limiting pathogen growth.
Immune System Cells: Key Functions
  • Neutrophils: First responders, engulf pathogens, produce inflammatory chemicals.
  • Monocytes: Differentiate into macrophages or dendritic cells to present antigens.
  • Mast Cells/Basophils: Release histamines and cytokines; involved in allergic reactions.
  • Natural Killer Cells: Destroy infected or cancer cells directly.
Inflammation Response
  • Triggered by macrophages; increases blood flow, allows white blood cells to enter tissues.
  • Symptoms include redness, swelling, pain, and heat.

Adaptive Immunity

  • Involves a specific response to pathogens, utilizing immunological memory.
  • Associated Cells:
    • B cells (produce antibodies).
    • T cells (helper and cytotoxic types for mounting responses).
MHC Proteins
  • Present on cells, allowing recognition of self vs. non-self.
  • MHC I: Found on all nucleated cells; recognize self.
  • MHC II: Found on antigen-presenting cells (APCs); assist in activating lymphocytes.
B Cell Activation
  • Activated by pathogens and Helper T-cells; differentiate into plasma cells that secrete antibodies.
  • Produces both immediate immune responses and memory cells for future encounters.

Types of Adaptive Immunity

Active Immunity
  • Develops through exposure to pathogens (natural or artificial).
    • Naturally: Exposure to an infection.
    • Artificially: Vaccination.
Passive Immunity
  • Transfer of antibodies from another individual (short-term protection).
    • Naturally: From mother to child during breastfeeding.
    • Artificially: Injection of pre-formed antibodies.

Vaccination Types

Live and Killed Vaccines
  • Live Vaccines: Made from attenuated pathogens (e.g., measles, mumps), induce strong immune response.
  • Killed Vaccines: Non-replicating strains (e.g., influenza), require larger doses for effectiveness.
Toxoids
  • Inactivated toxins from pathogens (e.g., tetanus); stimulate immunity without causing disease.
Summary of Key Functions of Antibodies
  • Neutralization of pathogens, marking them for destruction (opsonization), agglutination of pathogens, and activation of the complement system.