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Chapter 1: The Immune System


  • Cells of the primitive innate immune system and the Ag-specific adaptive immune system act as a cooperative network to bring about a coordinated and tightly regulated immune response to foreign Ags 
  • The primitive innate immune system uses a limited pattern of recognition molecules and, although it retains no memory, is able to mount a rapid response 
  • The Ag-specific adaptive immune system recognises a huge diversity of different specific Ags and elicits a response that is highly specific and retains memory 
  • Diversity and Ag specificity in both the TCR and BCR result from somatic recombination and the random splicing of a selected number of gene segments 
  • When naïve B cells encounter an Ag, further Ag specificity is added by somatic hypermutation in the GC of secondary lymphoid organs 
  • Only the most avid Ag-binding cells mature to become either Ab-producing plasma cells or memory B cells 
  • Abs may switch to different classes with differing effector functions and tissue locations while retaining the same Ag specificity in their variable regions 
  • In response to Ags, T cells differentiate to effector T cells that may augment the immune response, cytotoxic T cells that destroy altered self-cells, or regulatory T cells 
  • CKs regulate the immune response by autocrine, paracrine and endocrine mechanisms 
  • Cooperative interactions of both facets of the immune response result in efficient effector mechanisms that clear foreign Ags with residual immunological memory 

Further Reading

Immune System Activity

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