macrophage

Physiology

(noun)

A white blood cell that phagocytizes necrotic cell debris and foreign material, including viruses, bacteria, and tattoo ink. It presents foreign antigens on MHC II to lymphocytes. Part of the innate immune system.

Related Terms

Biology

(noun)

a white blood cell that phagocytizes necrotic cell debris and foreign material, including viruses, bacteria, and tattoo ink; part of the innate immune system

Related Terms

Examples of macrophage in the following topics:

  • Macrophages

    • Phagocytosis is a front-line defense against pathogen attack requiring the concerted action of macrophages.
    • Macrophages are antigen presenting cells that actively phagocytose large particles .
    • Resident macrophages become adapted to perform particular functions in different organs; so that brain macrophages (microglia) are very different from alveolar macrophages of the lung, Kupffer cells of the liver, or the largest tissue macrophage population, those lining the wall of the gut.
    • The macrophage then has the task of clearing both the dead pathogens and the dead neutrophils.
    • The process of recruitment of neutrophils and macrophages involves the resident macrophages which act as sentinels.

  • Phagocyte Migration and Phagocytosis

    • Dendritic cells and macrophages, on the other hand, are not so fast, and phagocytosis can take many hours in these cells.
    • All phagocytes, and especially macrophages, exist in degrees of readiness.
    • Macrophages are usually relatively dormant in the tissues and proliferate slowly.
    • In this state, macrophages are good antigen presenters and killers.
    • When they receive signals from macrophages at the sites of inflammation, they slow down and leave the blood.

  • Superantigens

    • Parts of a bacterium or a virus are usually recognized by the macrophage cells of the immune system.
    • The macrophage ingests the foreign invaders and breaks them down.
    • Then the macrophage takes parts of the broken-down invader or other molecules that it ingested and posts the fragments on the outside of the cell using a major histocompatibility complex (MHC) to hold the fragment.
    • This excess amount of IFN-gamma is in turn what activates the macrophages.

  • Phagocytes

    • The main types of phagocytes are monocytes, macrophages, neutrophils, tissue dendritic cells, and mast cells.
    • Mature macrophages are derived from monocytes, granulocyte stem cells, or the cell division of pre-existing macrophages.
    • Macrophages do not have granules, but contain many lysosomes.
    • Macrophages cause inflammation through the production of interleukin-1, interleukin-6, and TNF-alpha.
    • Neutrophils die after phagocytosis, becoming pus that is later cleaned up by macrophages.

  • Types of Cytokines Participating in Immune Response

    • They can activate macrophages and natural killer (NK) cells to attack and lyse virus-infected cells.
    • One common interferon is IFN-gamma, a pyrogen involved in inflammatory response and macrophage and NK cell activation.
    • This category also includes cytokines that are only involved in leukocyte migration, such as CCL2 which causes monocyte chemotaxis and stimulates its differentiation into macrophages inside of tissues.
    • It is a protein released by NK cells, macrophages, and helper T cells, typically in systemic immune responses.

  • Pathogen Recognition

    • A macrophage is a large, phagocytic cell that engulfs foreign particles and pathogens.
    • Macrophages recognize PAMPs via complementary pattern recognition receptors (PRRs).
    • Both macrophages and dendritic cells engulf pathogens and cellular debris through phagocytosis.
    • Monocytes mature into macrophages.
    • Neutrophils and macrophages also consume invading bacteria by phagocytosis.

  • Types of WBCs

    • The different types of white blood cells (leukocytes) include neutrophils, basophils, eosinophils, lymphocytes, monocytes, and macrophages.
    • Monocytes are large leukocytes that differentiate into macrophages and dendritic cells under varying conditions, while performing similar functions in phagocytosis and antigen presentation (the process by which molecular components are presented to lymphocytes to stimulate an adaptive immune response).
    • Macrophages are monocytes that have migrated out of the blood stream and into the internal body tissues.

  • Type IV (Delayed Cell-Mediated) Reactions

    • 2. activating macrophages and natural killer cells, enabling them to destroy pathogens
    • The antigen-presenting cells in this case are macrophages that secrete IL-12, which stimulates the proliferation of further CD4+ Th1 cells.
    • Activated CD8+ T cells destroy target cells on contact, whereas activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.

  • Cytotoxic T Lymphocytes and Mucosal Surfaces

    • Approximately 0.1 percent of all cells in the blood are leukocytes, which include monocytes (the precursor of macrophages) and lymphocytes.
    • Lymph nodes scattered throughout the body house large populations of T and B cells, dendritic cells, and macrophages .
    • The spleen houses B and T cells, macrophages, dendritic cells, and NK cells .

  • White Blood Cells

    • Some white blood cells become macrophages that either stay at the same site or move through the blood stream and gather at sites of infection or inflammation where they are attracted by chemical signals from foreign particles and damaged cells.
    • After the HIV virus replicates, it is transmitted directly from the infected T cell to macrophages.
    • Monocytes differentiate into macrophages and dendritic cells, which in turn respond to infection or injury.