Introduction to the Innate Immune Response

Explain immediate and induced innate immune responses

The immune system comprises both innate and adaptive immune responses. Innate immunity occurs naturally because of genetic factors or physiology; it is not induced by infection or vaccination but works to reduce the workload for the adaptive immune response. Both the innate and adaptive levels of the immune response involve secreted proteins, receptor-mediated signaling, and intricate cell-to-cell communication. The innate immune system developed early in animal evolution, roughly a billion years ago, as an essential response to infection. Innate immunity has a limited number of specific targets: any pathogenic threat triggers a consistent sequence of events that can identify the type of pathogen and either clear the infection independently or mobilize a highly specialized adaptive immune response. For example, tears and mucus secretions contain microbicidal factors.

What You’ll Learn to Do

  • Describe physical and chemical immune barriers
  • Describe different ways that host organisms recognize and combat pathogens
  • Discuss natural killer cells
  • Summarize how the proteins in a complement system function to destroy extracellular pathogens

Learning Activities

The learning activities for this section include the following:

  • Physical and Chemical Barriers
  • Pathogen Recognition
  • Natural Killer Cells
  • Complement System
  • Self Check: The Innate Immune Response