Download Definition of Immunologic Terms

Immunology Textbooks

Immunobiology, 6th edition, Janeway et al., Garland Science Publishing

Immunology, 5th edition, Goldsby et al., WH Freeman

Cellular and Molecular Immunology, 5th edition, Abbas and Lichtman, WB Saunders Company
Definition of Immunologic Terms
On-line dictionaries: www.nlm.nih.gov/medlineplus/mplusdictionary.html and www.medicinenet.com
o Acquired immunity: immune response specific for an antigen that is mediated by T and/or B
cells
o Alloantigen: a protein expressed by a foreign tissue that is recognized by the immune system
o Antibody (or immunoglobulin): protein produced by B cells which binds antigen in an immune
response. Monoclonal vs polyclonal refers to either a single antibody with a single specificity for
antigen (monoclonal) vs a mixture of antibodies with different specificities for antigen
(polyclonal).
o Antigen: a foreign substance, usually a protein or carbohydrate, that can be recognized by the
immune system
o Apoptosis: normal process of cell self-destruction, also called programmed cell death.
o Antigen presenting cell (APC): A cell that presents antigen in a form that T cells can recognize
it. To some extent, all cells with Class I HLA molecules can present intracellular antigen. Cells
that express Class II HLA molecules (e.g., dendritic cells, macrophages, B cells) are termed
“professional” APC.
o Antigen processing: An intracellular breakdown of foreign proteins into small pieces (peptides)
for binding by HLA molecules and presentation to T cells.
o Autoimmunity: a condition in which the body produces an immune response against itself
o B lymphocyte (B cell): A lymphocytes capable of producing antibodies
o CD: cluster of differentiation, used to identify specific cell surface molecules when appearing
with a number (e.g., CD4 or CD8); these molecules serve as markers to identify cell types (e.g., a
hematopoietic stem cell has CD34 on its surface, a T cell has CD3).
o Cellular immunity: part of the immune response that is mediated primarily by T cells
o Chemokine: cytokines that cause immune system cells to move into sites of inflammation (i.e.,
they are chemotactic)
o Costimulation: The delivery of a second signal by an antigen-presenting cell that induces the T
cell to produce cytokines and become activated. The first signal is delivered by a T cell receptor
recognizing antigen-HLA complexes.
o Cytokine: proteins secreted by cells of the immune system which affect the immune activities of
those cells and other cells in the vicinity. Examples of cytokines include interleukin 2 (IL-2),
tumor necrosis factor (TNF), and interferon (IFN) gamma.
o Dendritic cell: Professional antigen-presenting cell
o Education: The process by which immune system cells learn the difference between self tissue
and nonself (bacteria, grafted tissue). Much of the T cell education takes place in the thymus.
o Hematopoiesis: the formation of blood cells
o Hematopoietic growth factors: proteins produced by various cell types that promote the
differentiation of bone marrow stem cells (e.g., GM-CSF granulocyte, macrophage colonystimulating factor)
o Human leukocyte antigen (HLA): proteins specified by genes in the major histocompatibility
complex in humans that control the compatibility of transplanted tissue. There are two types of
HLA (or MHC) proteins, class I (HLA-A, HLA-B, HLA-C) and class II (HLA-DR, HLA-DQ,
HLA-DP).
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o Humoral immunity: the part of the immune response that involves antibodies produced by B
cells
o Immunogen: an antigen that stimulates an immune response
o Innate immunity: Nonspecific form of immunity that is naturally present and is not due to prior
sensitization to antigen (e.g., skin, acid lining of gut, phagocytic cells, NK cells)
o Inflammation: a local response (redness, pain, swelling, immune cell infiltration) to cellular
injury
o Killer immunoglobulin-like receptor (KIR): receptors expressed on the surface of NK cells that
detect the loss of HLA from the cell surface.
o Lymphocyte: immune system cell that originate from hematopoietic stem cells and differentiate
in the thymus or bone marrow. Lymphocytes make up 20-30 percent of the white blood cells of
normal human blood. Lymphocytes include B, T, and NK cells.
o Lymphoid organs: thymus, spleen, tonsils, lymph nodes, and bone marrow. The primary organs,
bone marrow and thymus, are the sites of differentiation of B cells and T cells. The secondary
lymphoid organs are the sites of antigen recognition and lymphocyte expansion during an immune
response.
o Lymphoid system: the part of the circulatory system that collects fluids and proteins that have
escaped from cells and tissues and returns them to the blood. It includes phagocytes that remove
cellular debris and foreign substances and primary and secondary lymphoid organs.
o Macrophage: a phagocytic cell that protects the body from infection, it is derived from a
monocyte
o Major histocompatibility complex (MHC): a group of genes found on chromosome 6 that
includes HLA
o Minor histocompatibility antigen: polymorphic proteins, other than HLA, that may stimulate the
recognition of foreign tissue during transplantation.
o Natural killer (NK) cell: a lymphocyte capable of killing a tumor or virus-infected cell without
prior sensitization.
o Neutrophil: important phagocytic white blood cell
o Phagocytosis: the engulfing and usually the destruction of particulate matter (eg bacteria) by cells
called phagocytes.
o Stem cell: Self-renewing, pluripotent cell with the potential to differentiate into many different
cell types.
o T cell receptor for antigen: a highly specific cell-surface antigen receptors on a T cell which
recognizes specific HLA-antigen complexes and activates T cells.
o Th1, Th2: Two classes of T-helper cells: Th1 cells activate other T cells to yield cellular
inflammatory responses. Th2 cells stimulate B cells to produce antibodies. Cytokines influence
whether one or the other response is generated while inhibiting the other.
o Thymus: a gland where T cells develop an are “educated” to distinguish “self” from “nonself”
o T lymphocyte (T cell): a lymphocyte that may control initiation (helper T cell) or suppression
(suppressor or regulatory T cell) of cellular or humoral immunity. Cytotoxic T cells lyse tumor
cells or cells infected with virus.
o Tolerance: loss of an immune response to a substance so that it is recognized as “self”
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