BSI: Immunology Glossary

  1. Activated Macrophages
    Macrophages whose killing ability has been enhanced by cytokines.

    • This is particularly true for:
    • IL-2
    • Interferon-gamma
  2. Antigen-Presenting Cells (APC)
    Cells that present antigen, complexed with MHC proteins, on their surface to T-cells.
  3. B Cells
    Lymphocytes that, upon activation, proliferate and differentiate into antibody-secreting plasma cells.

    B Cells provide major defense against bacteria, viruses and toxins in the extracellular fluid (ECF).

    B Cells can function as antigen presenting cells to helper T cells.
  4. Cytotoxic T Cells
    The class of T lymphocytes that, upon activation by specific antigen, directly attack the cells bearing that type of antigen.

    Cytotoxic T cells are major killers of virus-infected cells and cancer cells.

    Cytotoxic T cells bind antigen associated with class I MHC proteins.
  5. Eosinophils
    Leukocytes involved in destruction of parasites and in immediate hypersensitivity reactions (allergic reactions).
  6. Helper T Cells
    The class of T cells that, via secreted cytokines, play a stimulatory role in the activation of B cells and cytotoxic T cells.

    They can also activate Natural Killer (NK) cells and macrophages.

    Helper T cells bind antigen associated with Class II MHC proteins.
  7. Lymphocytes
    They type of leukocyte responsible for specific immune defenses.

    Categorized mainly as B cells, T cells, and Natural Killer (NK) cells.
  8. Macrophages
    • Cell type that:
    • (1) functions as a phagocyte
    • (2) processes and presents antigen to Helper T cells
    • (3) secretes cytokines involved in inflammation, activation of lymphocytes, and the systemic acute phase response to infection or injury
  9. Macrophage like-cells
    Several cell types that exert functions like those of macrophages.
  10. Mast Cells
    Tissue cells that bind IgE and release inflammatory mediators in response to parasites and immediate hypersensitivity reactions (allergic reactions).
  11. Memory Cells
    B cells and cytotoxic T cells that differentiate during an initial immune response and respond rapidly during a subsequent exposure to the same antigen.
  12. Monocytes
    A type of leukocyte that leaves the bloodstream and is transformed into a macrophage.

    A monocyte has functions similar to that of a macrophage, except it can't handle the capacity of phagocytosis to the degree that macrophages perform.
  13. Natural Killer (NK) Cells
    Class of lymphocytes that bind to cells bearing foreign antigens without specific recognition and kill them directly.

    Major targets are virus-infected cells and cancer cells.

    NK cells participate in antibody-dependent cellular cytotoxicity (ADCC).
  14. Neutrophils
    Leukocytes that function as phagocytes and also release chemicals involved in inflammation.
  15. Plasma Cells
    Cells that differentiate from activated B lymphocytes and secrete antibodies.
  16. T Cells
    Lymphcytes derived from precursors that differentiated in the thymus.
  17. Acute Phase Proteins
    Group of proteins secreted by the liver during systemic response to injury or infection.

    Stimulus for their secretion is IL-1, IL-6 and other cytokines.
  18. Antibodies
    Immunoglobulins secreted by plasma cells.

    They combine with the type of antigen that stimulated their production and direct an attack against the antigen or a cell bearing it.
  19. C1
    The first protein in the classical complement pathway.
  20. Chemoattractants
    Chemoattractants: A general name given to any chemical mediator that stimulates chemotaxis of neutrophils or other leukocytes.

    Chemokines: Any cytokine that functions as a chemoattractant.

    Chemotaxin: A synonym for chemoattractant.
  21. Complement
    A group of plasma proteins that, upon activation, kill microbes directly and facilitate the various steps of the inflammatory process, including phagocytosis.

    The classical complement pathway is triggered by antigen-antibody complexes, whereas the alternate pathway can operate independently of antibody.
  22. C-reactive protein
    One of several proteins that function as non-specific opsonins.

    Production by the liver is increased during the acute phase response.
  23. Cytokines
    General term for protein messengers that regulate immune responses.

    Cytokines are secreted by macrophages, monocytes, lymphocytes, neutrophils, and several non-immune cell types.

    They function both locally and as hormones.

    Cytokines are peptides that, in immune and inflammatory reactions, are released from and regulate the action of inflammatory and immune system cells.

    The cytokine superfamily includes the interferons, numerous interleukins, tumor necrosis factor (TNF), various growth factors, the chemokines and the colony stimulating factors (CSF).
  24. Eicosanoids
    General term for products of arachidonic acid metabolism (prostaglandins, thromboxanes, leukotrienes).

    They function as important inflammatory mediators.
  25. Histamine
    An inflammatory mediator secreted mainly by mast cells.

    Acts on microcirculation to cause vasodilation and increased permeability to protein.
  26. IgA
    The class of antibodies secreted by the lining of the body's various "tracts."
  27. IgD
    A class of antibodies whose function is unknown.
  28. IgE
    The class of antibodies that mediate immediate hypersensitivity (allergic reactions) and resistance to parasites.
  29. IgG
    The most abundant class of plasma antibodies.
  30. IgM
    A class of antibodies that is produced first in all immune responses. Along with IgG, it provides the bulk of specific humoral (blood) immunity against bacteria and viruses.
  31. Immunoglobulin (Ig)
    Proteins that function as B cell receptors and antibodies.

    The five major classes are IgA, IgD, IgE, IgG and IgM.
  32. Interferon
    Group of cytokines that non-specifically inhibits viral replication.

    Interferon-gamma also stimulates the killing ability of NK cells and macrophages. It activates macrophages and increases expression of class I and class II and MHC antigen processing and presentation.
  33. Interleukin 1 (IL-1)
    Cytokine secreted by macrophages (and other cells) that activates helper T cells, exerts many inflammatory effects, and mediates many of the systemic acute phase responses, including fever.

    There are two types of IL-1's: alpha and beta.

    They have a wide variety of biological effects. For example, they activate endothelium, lymphocytes and stimulate neutrophil production.
  34. Interleukin 2 (IL-2)
    Cytokine secreted by activated helper T cells that causes helper T cells, cytotoxic T cells, and NK cells to proliferate, and causes activation of macrophages.

    Growth factor for activated T cells. Induce synthesis of other cytokines. Activates cytotoxic T cells and NK cells.
  35. Interleukin 3 (IL-3)
    Growth factor for progenitor hematopoietic cells.
  36. Interleukin 4 (IL-4)
    Promotes growth and survival of T, B and mast cells.

    Causes TH2 cell differentiation.

    Activates B cells and eosinophils and induces IgE-type responses.
  37. Interleukin 5 (IL-5)
    Induces eosinophil growth and differentiation.

    Induces IgA production in B cells.
  38. Interleukin 6 (IL-6)
    Cytokine secreted by macrophages (and other cells) that exerts multiple effects on immune system cells, inflammation, and the acute phase response.

    Stimulates the liver to produce acute phase response. Induces proliferation of antibody producing cells.
  39. Interleukin 7 (IL-7)
    Stimulates pre-B cells and thymocyte development and proliferation.
  40. Interleukin 8 (IL-8)
    Chemoattracts neutrophils and T lymphocytes.

    Regulates lymphocyte homing and neutrophil infiltration.
  41. Interleukin 10 (IL-10)
    Decreases inflammation by inhibiting TH1 cells and release of IL-12 from macrophages.
  42. Interleukin 12 (IL-12)
    Induces TH1 cell differentiation and IFN-gamma synthesis by T and NK cells. Enhances NK cytotoxicity.
  43. Kinins
    Peptides that split from kininogens in inflamed areas and facilitate the vascular changes associated with inflammation.

    They also activate neuronal pain receptors.
  44. Leukotrienes
    A class of eicosanoids that are generated by the lipoxygenase pathway and function as inflammatory mediators.
  45. Membrane Attack Complex (MAC)
    Group of complement proteins that form channels in the surface of a microbe, making it leaky and killing it.

    In other words, a "MAC" attack punches holes in invaders and then fills them full of immune cells that eat it from the inside out.
  46. Natural Antibodies
    Antibodies to the erythrocyte antigens (of the A or B type).
  47. Opsonin
    General name given to any chemical mediator that promotes phagocytosis.
  48. Perforin
    Protein secreted by cytotoxic T cells and NK cells that forms channels in the plasma membrane of the target cell, making it leaky and killing it.

    Its structure and function are similar to that of the MAC in the complement system.
  49. Tumor Necrosis Factor (TNF)
    Cytokine secreted by macrophages (and other cells) that has many of the same actions as IL-1.

    Induces inflammation, fever, and acute phase response. Activates neutrophils and endothelial cells. Kills cells through apoptosis.
  50. Colony Stimulating Factors (CSFs)
    Promotes neutrophil, eosinophil, and macrophage maturation and growth. Activates mature granulocytes. Promotes growth and maturation of monocytes.
  51. Granulocyte-macrophage CSF
    Promotes growth and maturation of neutrophils.
  52. Macrophage CSF
    Promotes growth and maturation of monocytes.
  53. Mediators derived from Phospholipids
    • The main phospholipid derived mediators are:
    • (1) the eicosanoids (prostanoids and leukotrienes)
    • (2) platelet activating factor (PAF)

    The eicosanoids are derivatives of arachidonate that can be released from phospholipid by phospholipase action.
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BSI: Immunology Glossary
1/19/2011: Immunology Glossary