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Chapter 1: The Immune System


  • Cells of the primitive innate immune system and the antigen-specific adaptive immune system act as a cooperative network to bring about a coordinated and tightly regulated immune response to foreign antigens
  • The former uses a limited pattern of recognition molecules and, although it retains no memory, is able to mount a rapid response
  • The latter recognises a huge diversity of different specific antigens and elicits a response that is highly specific and retains memory
  • Diversity and antigen specificity in both the TCR and BCR result from somatic recombination and the random splicing of a selected number of gene segments
  • When naive B-cells encounter an antigen, further antigen specificity is added by somatic hypermutation in the germinal centre of secondary lymphoid organs
  • Only the most avidly antigen-binding cells mature to become either antibody-producing plasma cells or memory B-cells
  • Antibodies may switch to different classes with differing effector functions and tissue locations while retaining the same antigen specificity in their variable regions
  • In response to antigen, 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
  • Cytokines 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 antigen with residual immunological memory

Further Reading

Immune System Activity

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