phagocyte

(noun)

A cell of the immune system, such as a neutrophil, macrophage or dendritic cell, that engulfs and destroys viruses, bacteria and waste materials, or, in the case of mature dendritic cells, displays antigens from invading pathogens to cells of the lymphoid lineage.

Related Terms

Examples of phagocyte in the following topics:

  • Microbial Evasion of Phagocytosis

    • Pathogens have evolved mechanisms to evade capture by phagocytes in the immune system.
    • Pathogenic bacteria and protozoa have developed a variety of methods to resist attacks by phagocytes (phagocytosis), and many actually survive and replicate within phagocytic cells.
    • There are several ways bacteria avoid contact with phagocytes.
    • First, they grow in sites that phagocytes are not capable of traveling to (e.g. the surface of unbroken skin).
    • Bacteria have developed several ways of killing phagocytes.

  • Phagocytes

    • Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles and help initiate an immune response.
    • Most phagocytes are derived from stem cells in the bone marrow.
    • The main types of phagocytes monocytes, macrophages, neutrophils, tissue dendritic cells, and mast cells.
    • Phagocytes derive from stem cells in the bone marrow.
    • Describe the types of phagocytes and their role in initiating an immune response

  • Neuroglia of the Peripheral Nervous System

    • They also perform phagocytic functions and clear cellular debris, allowing for the regrowth of PNS neurons.

  • WBC Function

    • The antibodies bind to pathogens to opsonize (mark) them for phagocytes to engulf, neutralize them, or start a complement cascade in which proteins form a membrane attack complex to lyse the pathogen.

  • Spleen

    • The spleen, similar to a large lymph node, acts primarily as a blood filter in the mononuclear phagocyte system of the immune system.
    • When blood passes through the red pulp of the spleen, healthy blood cells will easily pass while, older red blood cells will be caught and the macrophages within will phagocytize them.

  • Structure and Function of Antibodies

    • In some isotypes, the tail end of the antibody is called the constant region, which faces away from the "Y-shaped" paratobe ends, functions as an Fc tail that phagocytes can bind to.
    • This is because it expresses a tail for Fc receptors on phagocytes to bind to, which activates phagocytosis.
    • The immune cell will then bind to the antibody's Fc tail instead of the pathogen itself, which speed up the process of finding pathogens to phagocytize.

  • Role of the Complement System in Immunity

    • The complement system is the ability of antibodies and phagocytic cells to remove pathogens from an organism.
    • The complement system helps or "complements" the ability of antibodies and phagocytic cells to clear pathogens from an organism.

  • Steps of Tissue Repair

    • In the inflammatory phase, phagocytes remove debris and bacteria.

  • Antigenic Determinants and Processing Pathways

    • Antigen processing occurs within an APC that phagocytizes an antigen and then digests it through fragmentation (proteolysis) of the antigen protein, association of the fragments with MHC molecules, and expression of the peptide-MHC molecules at the cell surface where they can be recognized by the T cell receptor on a T cell during antigen presentation.
    • First, pathogens are phagocytized, and then endosomes within the cell break down antigens with proteases, which then combine with MHC II.

  • Natural Killer Cells

    • Unlike phagocytes, NK cells do not need their targets to be opsonized (marked) by antibodies before they can act allowing for a much faster immune reaction, however opsonins do speed up the process.
    • Cellular lysis causes necrosis of that cell, in which the DNA and cell components degrade into debris that must be phagocytized by macrophages.