Chapter 2 - Cells And Organs Of The Immune System

Front 1

Leukocytes

Back 1

a white blood cell;
the category includes lymphocytes, granulocytes, platelets, monocytes, and macrophages

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Hematopoietic stem cell (HSC)

Back 2

the cell type from which all lineages of blood cells arise

Front 3

Stem cells

Back 3

a cell from which differentiated cells arise

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Hematopoiesis

Back 4

the formation and differentiation of blood cells

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Lymphoid progenitor cell

Back 5

a cell committed to the lymphoid lineage from which all lymphocytes arise

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Myeloid progenitor cell

Back 6

a cell that gives rise to cells of the myeloid lineage

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Progenitor cells

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a cell that has lost the capacity for self renewal and is committed to the generation of a particular cell lineage

Front 8

Cytokine

Back 8

any of numerous secreted, low molecular weight proteins that regulate the intensity and duration of the immune response by exerting a variety of effects on lymphocytes and other immune cells

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Stromal cells

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a nonhematopoietic cell that supports the growth and differentiation of hematopoietic cells

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Hematopoietic-inducing microenvironment (HIM)

Back 10

an anatomical site that contains all of the cells and cellular factors required for the generation and development of blood cells

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Colony-stimulating factors (CSFs)

Back 11

proteins that are able to induce and support the growth and development of distinct hematopoietic cell lines

Front 12

Erythropoietin (EPO)

Back 12

a cytokine that induces the commitment of progenitor cells to the erythroid lineage

Front 13

GATA-2 gene

Back 13

a gene encoding a transcription factor that is essential for the development of several hematopoietic cell lineages, including the lymphoid, erythroid and myeloid lineages

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Ikaros

Back 14

a transcription factor required for the development of all lymphoid cell lineages

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Programmed cell death

Back 15

an induced and ordered process in which the cell actively participates in bringing about its own death

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Apoptosis

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morphologic changes associated with programmed cell death, including nuclear fragmentation, blebbing, and release of apoptotic bodies, which are phagocytosed;
in contrast to necrosis, it does not result in damage to surrounding cells

Front 17

Differentiation antigen

Back 17

a cell-surface marker that is expressed only during a particular developmental stage or by a particular cell lineage

Front 18

Natural killer cells

Back 18

a class of large granular cytotoxic lymphocytes that do not have T- or B-cell receptors;
antibody-independent killers of tumor cells and also can participate in ADCC

Front 19

Lymphoblasts

Back 19

a proliferating lymphocyte

Front 20

Naive lymphocytes

Back 20

denoting mature B and T cells that have not encountered antigen;
synonymous with unprimed and virgin

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Effector cells

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any cell capable of mediating an immune function (e.g., activated T(H) cells, CTLs, and plasma cells)

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Memory cells

Back 22

lymphocytes generated following encounters with antigen that are characteristically long lived; they are more readily stimulated than naive lymphocytes and mediate a secondary immune response to subsequent encounters with the antigen

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Plasma cells

Back 23

the antibody-secreting effector cell of the B lineage

Front 24

Cluster of differentiation (CD)

Back 24

a collection of monoclonal antibodies that all recognize an antigen found on a particular differntiated cell type or types; each of the antigens recognized by such a collection of antibodies is called a CD marker and assigned a unique identifying number

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T(H)1 response

Back 25

this response produces a cytokine profile that supports inflammation and cell mediated responses;
antagonistic to the T(H)2 response

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T(H)2 response

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this response produces a cytokine profile that activates mainly immune responses that depend upon antibodies;
antagonistic to the T(H)1 response

Front 27

Cytotoxic T lymphocyte (CTL)

Back 27

an effector T cell (usually CD8+) that can mediate the lysis of target cells bearing antigenic peptides complexed with an MHC molecule;
usually arises from an antigen-activated T(C) cell

Front 28

T suppressor cells

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a population of T cells postulated to be distinct from T(H) and T(C)cells that suppress the humoral and cell-mediated branches of the immune system in an antigen-specific manner

Front 29

Antibody-dependent cell-mediated cytotoxicity (ADCC)

Back 29

a cell-mediated reaction in which nonspecific cytotoxic cells that express Fc receptors (e.g., NK cells, neutrophils, macrophages) recognize bound antibody on a target cell and subsequently cause lysis of the target cell

Front 30

NK1-T cell

Back 30

a lymphocyte with some of the characteristics of T cells (it has TCRs) as well as those of NK cells

Front 31

Monocyte

Back 31

a mononuclear phagocytic leukocyte that circulates briefly in the bloodstream before migrating into the tissues where it becomes a macrophage

Front 32

Macrophage

Back 32

mononuclear phagocytic leukocytes that play roles in adaptive and in innate immunity;
some are migratory and others are fixed in tissues

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Chemotaxis

Back 33

directional movement of cells up the concentration gradient

Front 34

Pseudopodia

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membrane protrusions that extend from motile and phagocytosing cells

Front 35

Phagosome

Back 35

intracellular vacuole containing ingested particulate materials;
formed by the fusion of pseudopodia around a particle undergoing phagocytosis

Front 36

Lysosome

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a small cytoplasmic vesicle found in many types of cells that contains hydrolytic enzymes, which play an important role in the degradation of material ingested by phagocytosis and endocytosis

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Phagolysosome

Back 37

an intracellular body formed by the fusion of a phagosome with a lysosome

Front 38

Exocytosis

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process by which cells release molecules (e.g., cytokines, lytic enzymes, degradation products) contained within a membrane-bound vesicle by fusion of the vesicle with the plasma membrane

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Opsonin

Back 39

a substance that promotes the phagocytosis of antigens by binding to them

Front 40

Opsonization

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deposition of opsonins on an antigen, thereby promoting a stable adhesive contact with an appropriate phagocytic cell

Front 41

Reactive oxygen intermediates (ROIs)

Back 41

highly reactive compounds such as superoxide anion, hydroxyl radicals, and hydrogen peroxide that are formed under many conditions in cells and tissues

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Reactive nitrogen intermediates

Back 42

highly cytotoxic antimicrobial compounds formed by the combination of oxygen and nitrogen within phagocytes such as neutrophils and macrophages

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Respiratory burst

Back 43

a metabolic process in activated phagocytes in which the rapid uptake of oxygen is used to produce reactive oxygen intermediates that are toxic to ingested microorganisms

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Nitric Oxide synthetase

Back 44

an enzyme that synthesizes nitric oxide from the amino acid L-arginine

Front 45

Nitric oxide

Back 45

a gas that plays important roles in intercellular signaling

Front 46

Lysozyme

Back 46

an enzyme present in tears, saliva, and mucous secretions that digests mucopeptides in bacterial cell walls and thus functions as a nonspecific antibacterial agent

Front 47

Defensins

Back 47

cysteine-rich, positively charged, antimicrobial peptides that contain 25-35 amino acids and are found in macrophages and neutrophils

Front 48

Tumor necrosis factors (TNFs)

Back 48

two related cytokines produced by marophages and some T cells;
cytotoxic to tumor cells but not to normal cells;
also play a role in inflammatory response

Front 49

Complement

Back 49

a group of serum proteins that participates in an enzymatic cascade, ultimately generating the cytolytic membrane attack complex

Front 50

Granulocytes

Back 50

any leukocyte that contains cytoplasmic granules, particularly the basophil, eosinophil, and neutrophil

Front 51

Neutrophil

Back 51

a circulating, phagocytic granulocyte involved early in the inflammatory response;
expresses Fc receptors and can participate in antibody-dependent cell-mediated cytotoxicity;
the most numerous WBCs in the circulation

Front 52

Eosinophil

Back 52

motile, somewhat phagocytic granulocytes that can migrate from blood to tissue spaces;
have large numbers of IgE receptors and are highly granular; that to play a role in the defense against parasitic organisms such as roundworms

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Basophil

Back 53

a nonphagocytic granulocyte that expresses Fc receptors for IgE;
antigen-mediated cross-linkage of bound IgE induces degranulation of basophils

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Leukocytosis

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an abnormally large number of leukocytes, usually associated with acute infection;
counts greater than 10,000/cc may be considered leukocytosis

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Extravasation

Back 55

movement of blood cells through an unruptured vessel wall into the surrounding tissue, particularly at sites of inflammation

Front 56

Chemotactic factor

Back 56

an agent that can cuase leukocytes to move up its concentration gradient

Front 57

Dendritic cell

Back 57

bone-marrow derived cells that descend through the myeloid and lymphoid lineages and are specialized for antigen presentation to helper T cells

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Follicular dendritic cell

Back 58

a cell with extensive dendritic extensions that is found in the follicles of lymph nodes;
although they do not express MHC-II molecules, they are richly endowed with receptors for complement and Fc receptors for antibody;
of a lineage that is distinct from MHC-II bearing dendritic cells

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Primary lymphoid organs

Back 59

organs in which lymphocyte precursors mature into antigenically committed, immunocompetent cells;
in mammals, the bone marrow and thymus are the primary lymphoid organs in which B-cell and T-cell maturation occur, respectively

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Secondary lymphoid organs

Back 60

organs and tissues in which mature, immunocompetent lymphocytes encounter trapped antigens and are activated into effector cells;
in mammals, the lymph nodes, spleen, and MALT constitue the secondary lymphoid organs

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Tertiary lymphoid tissues

Back 61

tissues that normally contain few lymphoid cells, lack the elaborate organization of secondary lymphoid tissue, and import lymphoid cells during an inflammatory response

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Lymphatic system

Back 62

a network of vessels and nodes that convey lymph;
returns plasma-derived interstitial fluids to the blood stream and plays an important role in the integration of the immune system

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Immunocompetent

Back 63

denoting a mature lymphocyte that is capable of recognizing a specific antigen and mediating an immune response

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Thymus

Back 64

a primary lymphoid organ, located in the thoracic cavity, where T-cell maturation takes place

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Bone marrow

Back 65

the living tissue found within the hard exterior of bone

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Interstitial fluid

Back 66

fluid found in the space between cells of an organ or tissue

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Lymph

Back 67

interstitial fluid derived from blood plasma that contains a variety of small and large molecules, lymphocytes, and some other cells;
circulates through the lymphatic vessels

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Lymphatic vessels

Back 68

thinly walled vessels through which the fluid and cells of the lymphatic system moves through the lymph nodes and ultimately into the thoracic duct, where it joins the blood stream

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Thoracic duct

Back 69

the largest of the lymphatic vessels; returns lymph to the circulation by emptying into the left subclavian vein near the heart

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Primary follicle

Back 70

a lymphoid follicle, prior to stimulation with antigen, that contains a network of follicular dendritic cells and small resting B cells

Front 71

Secondary follicle

Back 71

a primary follicle after antigenic stimulation;
develops into a ring of concentrically packed B-cells surrounding a germinal center

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Germinal center

Back 72

a region within lymph nodes and the spleen where B-cell activation, proliferation, and differentiation occurs;
sites of intense B cell somatic mutation and selection

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Lymph nodes

Back 73

a small secondary lymphoid organ that contains lymphocytes, macrophages, and dendritic cells and serves as a site for filtration of foreign antigen and for activation and proliferation of lymphocytes

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Spleen

Back 74

secondary lymphoid organ where old erythrocytes are destroyed and blood-borne antigens are trapped and presented to lymhocytes in the PALS and marginal zone

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Red pulp

Back 75

portion of the spleen consisting of a network of sinusoids populated by macrophages and erythrocytes;
the site where old and defective red blood cells are destroyed

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White pulp

Back 76

portion of the spleen that surrounds the arteries, forming a periarteriolar lymphoid sheath populated mainly by T cells

Front 77

Mucosal-associated lymphoid tissue (MALT)

Back 77

lymphoid cells and tissues below the epithelial layer of the body's mucosal surfaces;
found in the gastrointestinal and reproductive tracts

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Tonsils

Back 78

nodular structures containing a meshwork of reticular cellsand fibers that contain lymphocytes, macrophages, granulocytes, and mast cells;
defend the body against antigens entering through nasal or oral routes

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Intraepithelial lymphocytes

Back 79

T cells found in the epithelial layer of organs and the GI tract

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M cells

Back 80

specialized cells of the intestinal mucosa and other sites, such as the urogential tract, that deliver antigen from the apical face of the cell to lymphocytes clustered in the pocket of its basolateral face

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Inductive site

Back 81

small regions of a mucus membrane that lie over organized lymphoid follicles and contain M cells