Cells in Innate and Adaptive Immunity

Immunity

• Immunity is the body's ability to defend itself against infectious agents, foreign cells, and abnormal body cells such as cancer cells.
• The immune system can differentiate 'self' from 'non-self'.

Innate Immunity

• Present before any exposure to pathogens and is effective from the time of birth.
• The first line of defense, always ready to provide immediate defense against invaders and damaged cells.
• Nonspecific, does not discriminate between kinds of foreign bodies.
• Quickly recognizes and responds to a broad range of microbes.
• Recognizes pathogen-associated molecular patterns (PAMPs) such as glycans and flagellin in bacteria cell walls.
• No memory, there is no recognition that an intruder has attacked before and therefore no immunological memory.
• Components include:
  • Physical and chemical barriers (e.g. skin, mucous membranes)
  • Inflammatory reaction
  • Phagocytosis
  • Natural killer cells
  • Protective proteins (e.g. complements, interferons)

Barriers to Entry

• Intact skin is a barrier that cannot normally be penetrated by viruses or bacteria.
• Mucous membranes lining the digestive, respiratory, and genitourinary tracts prevent the entry of harmful microbes.
• Cells of the mucous membranes produce mucus, a viscous fluid that traps microbes and other particles.
• The upper respiratory tract is lined by ciliated cells that sweep mucus and trapped particles or microbes into the throat.
• The acidic environment (low pH) of the stomach destroys most pathogens before they can enter the intestines.
• Normal flora (harmless bacteria) present in the intestine and other areas prevent colonization by pathogens.

Adaptive Immunity

• Characterized by the production of a very large number of diverse receptors on the surface of white blood cells.
• These receptors bind specifically to molecules called antigens.
• Interactions lead to activation of the immune response.
• Characteristics include:
  • The second line of defense.
  • Activated after exposure to pathogens.
  • Pathogen-specific.
  • Has memory.
• Enhanced after first exposure to the antigen, and the person becomes immune.

Cells Involved in Immunity

• Macrophages
• Neutrophils
• Dendritic cells
• Natural killer cells
• Complements
• Cytokines (signaling proteins that act like messengers between cells of the immune system)

Test your knowledge about the cells involved in innate and adaptive immunity. Learn about the differences between innate and adaptive immunity, including their characteristics and roles in the immune response.