INTRODUCTION TO THE IMMUNE SYSTEM

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INTRODUCTION TO THE IMMUNE SYSTEM

• Janet Liversidge
• Department of Ophthalmology
• Medical School
• j.liversidge_at_abdn.ac.uk

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Innate and adaptive immunity
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The course of a typical antibody response The
adaptive response takes 7-14 days to develop and
mount a specific, protective immune response
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An infection, and the response to it can be
divided into stages and involves soluble
mediators and cells of the immune system
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Circulating lymphocytes encounter antigen in
peripheral lymph nodes
The adaptive immune response develops in the
lymphoid tissues
Sentinel cells in the periphery pick up
pathogens and transport them to the draining
lymph node
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• The immune response is dynamic, involving cells
  re-circulating from the tissues via the
  lymphatics and blood system
• Innate immunity acts locally in the infected
  tissue,
• Adaptive immune responses develop in the lymphoid
  tissues,
• Effector cells multiply and migrate back to
  tissue.

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Cellular components of the immune system
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Myeloid cells in innate and adaptive immunity
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Phagocytic cells
Polymorphonuclear neutrophils
Blood monocytes
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Phagocytosis
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The mononuclear phagocyte system
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Mobilisation of defensive components of innate
immunity
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Macrophages and acute inflammation
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B cells need T cell help to make antibody
Lymphocytes mediate adaptive (pathogen specific)
immunity each cell has a unique antigen receptor
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Innate and adaptive (acquired) immunity are
integrated
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The response to an initial infection occurs in
three phases innate, early induced, adaptive.
SUMMARY
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Cells of the innate immune system, macrophages,
granulocytes, natural killer cells, immature B
cells

• Release of soluble components to opsinise
  phagocytosis
• Release of toxic granules to kill
  micro-organisms, parasites or virally infected
  cells
• Release of soluble mediators to attract other
  leukocytes to site of inflammation
• Removal of dead or dying cells
• Transfer of infectious or toxic material to lymph
  nodes to initiate adaptive immune response

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Cells of the adaptive immune system Dendritic
cells, T and B lymphocytes,

• Lymphocytes are generated with unique antigen
  receptors on their surface.
• Dendritic cells (and macrophages) present antigen
  to lymphocytes and provide activating signals
• Lymphocytes undergo clonal expansion and migrate
  back to area of infection as effector cells.
• T cytotoxic cells selectively kill virally
  infected cells
• T helper cells selectively help B cells produce
  large amounts of high affinity specific antibody.
  
• After infection, memory lymphocytes provide
  protective immunity

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Natural killer cells kill virally infected cells
Virally induced structures
IFN-g released by infected cell primesother
cells to kill it