Hormones

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Hormones involving the immune system consist of specific and nonspecific defences coordinated by two actions:

physical interaction – such as the displaying of antigens by the activated macrophages or helper T cells

the release of chemical messengers – such as the release of cytokines by many cell types

Immune system cytokines are classified according to their source. For instance, lymphokines are secreted by lymphocytes; and monokines are released by active macrophages and other antigen-presenting cells. The general term cytokine is preferable since lymphocytes, macrophages, and cells involved with nonspecific defences and tissue repair may secrete the same chemical messenger.

Chemical messengers

Interleukins are the most diverse and the most important. Massive production of interleukins can cause problems as severe as those of the primary infection. For example, in Lyme disease, the release of Interleukin II-1 by activated macrophages produce symptoms of fever, pain, skin rash, and arthritis that affect the entire body in response to a localized bacterial infection.
- II-1
  - stimulate T cells
  - promote inflammation
  - cause fever
- II-2 and II-12
  - stimulate T cells and NK cells
- II-3
  - stimulate blood cell production
- II-4, -5, -6, -7, -10, -11
  - promote B cells
  - stimulate plasma cell formation
  - stimulate antibody production
Interferons activate other cells to prevent the entrance of viruses and their replication. In other words, they interfere with viral activity. Interferons also stimulate NK cells and macrophages to resist the spread of viruses.
Tumor necrosis factors (TNF) slow tumor growth and kill sensitive tumor cells. TNF:
- stimulate the production of granulocytes;
- promote eosinophil activity;
- inhibit parasites and viruses;
- cause fever;
- increase T cell sensitivity to interleukins.
Phagocytic regulators include several cytokines that coordinate the specific and nonspecific defences by adjusting the activities of phagocytic cells. These cytokines include factors that attract free macrophages and microphages to an area and prevent their premature departure.
- Monocyte-chemotactic factor (MCF) attracts monocytes, activating them to macrophages.
- Macrophage-inhibitory factor (MIF) prevents macrophage migration from the area.
Colony-stimulating factors (CSFs) are produced by a wide variety of cells, including active T cells and fibroblasts. They stimulate production of blood cells in the bone marrow and lymphocytes in lymphoid tissues and organs.
- M-CSF stimulate activity in the monocyte-macrophage line.
- GM-CSF stimulate production of both macrophages and monocytes.
This page was updated in December 2005.