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Chapter 1: The Immune System

Immune System Activity Figure 1

Source: Singulex (link correct at time of publication; June 2015)

Cytokines (CK) are low molecular weight proteins that play a key role in the induction and regulation of the immune response.

Produced by a variety of cells, their actions are mediated through their respective receptors; they exert autocrine, paracrine, and endocrine effects.

CK regulate the intensity and duration of both the innate and adaptive immune response.

Immune System Activity Figure 2

Source: Wahl M. Muscular Dystrophy Association - Quest Magazine 2008 (15);4. (Last accessed on 1 june 2015)

The various individual facets of the immune response interact in a complex fashion to result in a coordinated response.

Following a rapid response by the cells of the innate system, the cells of the adaptive immune system recognise Ag, expanding and activating effectors.

APC, present throughout the body, internalise and process Ag, displaying part of it on their surface bound to a class II MHC molecule.

Immune System Activity Figure 3

Source: Casadevall A, et al. Nat Rev Microbiol 2004;2:695-703

This way APC carry cargos of foreign Ag to lymphoid organs, where they are recognised by Th cells which initiate the adaptive response.

All aspects of the adaptive response are initiated and controlled by T-cells. They recruit immunological effector mechanisms by direct contact or through CK.

Antibodies may cause direct cytotoxicity by activation of the complement cascade or by recruiting effector cells (NK, macrophages) that cause cell death.

Revision Questions

  1. What are cytokines and how do they exert their function?
  2. What is the role of the antigen-presenting cells?
  3. What mechanisms are employed by antibodies to result in dysfunctional cell death?
T-Cells and NK-Cells Summary and Further Reading

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