Basic Immunology

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Basic Immunology

• OBJECTIVE
• To provide the fundamentals of the immune
  response. The immune response is the host
  reaction to infection/invasion. It is important
  to understand the immune response when developing
  materials and devices to be implanted into the
  body.

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Background Cell Communication
Cells can communicate to each other through the
use of soluble chemicals, contacts and cell
membrane resident receptors.
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Intravascular Cells

• white blood cells

Granulocytes
neutrophil
eosinophil
basophil
lymphocyte
monocyte
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Host Defence

• The body is under constant attack by
  microorganisms in the environment.
• pathogen an infectious agent that causes
  disease
• Infectious disease occurs when a microorganism
  succeeds in evading or overwhelming host defenses
  to establish a local site of infection and
  replication. In order for a pathogen to enter
  the body it must first overcome the epithelium
  and then the innate immune response and the
  adaptive immune response.

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First Line of Defence

• Epithelial Tissue
• covers the whole surface of the body
• made up of closely packed cells
• can be divided into simple or stratified
• interior epithelium covered with a mucus layer

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Stratified Epithelium - Skin
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Innate Immune response

• If a pathogen breaches the epithelium,
• then the innate immune response begins.
• The cells of the immune system determine
• self from non-self by recognizing molecules
  on the microbe surface.
• Macrophages and dendritic cells are immune cells
  (phagocytes) that reside within the tissue.
  Neutrophils are phagocytes that reside in the
  blood but can extravasate into tissue during
  inflammation.
• There are circulating proteins, called
  complement, that either kill microbes or mark
  them for effective phagocytization.

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Phagocytosis

• Phagocytosis
• Engulfing and degradation or digestion of
  fragments of tissue or material
• long membrane evaginations, called pseudopodia.
• Ingestion forming a "phagosome," which moves
  toward the lysosome.
• Fusion of the lysosome and phagosome
  (phagolysosome), releasing lysosomal enzymes
• Digestion of the ingested material.
• Release of digestion products from the cell.

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Inflammatory Response

• Pathogen recognition and tissue damage begin an
  inflammation response. This is characterized by
  
• swelling
• pain
• redness
• heat
• Inflammation allows for neutrophil and plasma
  protein extravasation. Both of these effects
  aids the immune response.

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Diapedesis Movie
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Phagocytosis Movie
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Adaptive Immune Response

• The innate response triggers the cells of the
  adaptive immune response called lymphocytes.
  Lymphocytes are present in the blood and in the
  lymphatic system.

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Antigen Presenting Cells

• Dendritic cells and macrophages digest invading
  microbe and then present the antigen of the
  microbe to lymphocytes in lymphoid organs.

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Activation of T cells
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Activation of B cells
The role of B cells is to produce antibodies.
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Antibody
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Summary

• The immune system consists of
• biological barriers
• the phagocytic cells within tissues
• proteins in circulation called complement
• the lymphatic system
• lymphocytes such as B and T cells
• antibodies