33.1Innate Immune Response

The innate immune system serves as a first responder to pathogenic threats that bypass natural physical and chemical barriers of the body. Using a combination of cellular and molecular attacks, the innate immune system identifies the nature of a pathogen and responds with inflammation, phagocytosis, cytokine release, destruction by NK cells, and/or a complement system. When innate mechanisms are insufficient to clear an infection, the adaptive immune

adaptive immunity
immunity that has memory and occurs after exposure to an antigen either from a pathogen or a vaccination
affinity
attraction of molecular complementarity between antigen and antibody molecules
allergy
immune reaction that results from immediate hypersensitivities in which an antibody-mediated immune response occurs within minutes of exposure to a harmless antigen
antibody
protein that is produced by plasma cells after stimulation by an antigen; also known as an immunoglobulin

In this section, you will explore the following questions:

  • What is hypersensitivity?
  • What is autoimmunity, and what is an example of an autoimmune disease?

Connection for AP® Courses

Much of the information in this section is not within the scope for AP®. Immune systems can, at times, be defeated by pathogens. For example, some bacteria, including Streptococcus pneumoniae, surround themselves with a capsule that inhibits phagocytes from engulfing them and