The Immune System

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The Immune System

• The key primary lymphoid organs of the immune
  system are thymus and bone marrow
• Secondary lymphatic tissues such as spleen,
  tonsils, lymph vessels, lymph nodes, adenoids,
  and skin.

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Macrophage

• Macrophage A type of white blood that ingests
  (takes in) foreign material. Macrophages are key
  players in the immune response to foreign
  invaders such as infectious microorganisms.
• Macrophages help destroy bacteria, protozoa, and
  tumor cells. They also release substances that
  stimulate other cells of the immune system.
• And they are involved in antigen presentation. To
  do this, they carry the antigen on their surface
  and present it to a T cells.

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Neutrophis and macrophages (phagocytes)

• Engulf (phagocytose) and destroy
  micro-organisms

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Eosinophils

• Secrete factors which kill protozoa and worms

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• Natural killer cells

• Can lyse and kill cancer and virus infected body
  cells
• They do not engulf the cells but inject chemicals
  called perforins that open up channels and
  disintegrate the nucleus.

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Langerhans cells
Langerhans cells are dendritic cells in the skin.
Skin is an important barrier to infection and it
has been generally assumed that the Langerhans
cells only serve to warn the immune system of
skin pathogens.
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Dendritic cell

• There are two cell types with similar names but
  different functions. Cells of the dendritic cell
  (DC) lineage are bone marrow derived. In the skin
  they are known as Langerhans Cells (LC).
• These cells efficiently process antigen but
  cannot present it to T cells. LC have been shown
  to pick up antigen in skin and carry it via
  afferent lymphatic vessels to lymph nodes.
  Dendritic cells in lymph are known as "veiled"
  cells. In lymph nodes the cells, now known as
  tissue dendritic cells or interdigitating cells,
  may efficiently present antigen if they encounter
  the right T cell. In fact these are the best
  APC...............far fewer DC are required to
  initiate an immune response than any other APC.

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Mast cells (concentrated under the body surfaces)

• Release factors which increase blood flow and
  vascular permeability bringing components of
  immunity to the site of infection