FAQ

  1. What is Flow Cytometry? It is a Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.
  2. What is Cell Separation? It is lymphocyte separation by facs of flow cytometry.
  3. What is Cells, Cultured? It are Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.
  4. What is Antigens, CD? It are Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation.
  5. What is Green Fluorescent Proteins? It are Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.
  6. What is Apoptosis? It are One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.
  7. What is Cell Differentiation? It are Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.
  8. What is Cell Line, Tumor? It is a cell line derived from cultured tumor cells.
  9. What are Antibodies, Monoclonal? It are Antibodies produced by a single clone of cells.
  10. What is Cell Proliferation? It are All of the processes involved in increasing CELL NUMBER including CELL DIVISION.
  11. What is Stem Cells? It are Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.
  12. What is Reverse Transcriptase Polymerase Chain Reaction? It are A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.
  13. What is RNA, Messenger? It are RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
  14. What is Immunophenotyping? It are Process of classifying cells of the immune system based on structural and functional differences. The process is commonly used to analyze and sort T-lymphocytes into subsets based on CD antigens by the technique of flow cytometry.
  15. What is Cell Line? It are Established cell cultures that have the potential to propagate indefinitely.
  16. What is Mice, Inbred C57BL? It are
  17. What is T-Lymphocytes? It are Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
  18. What is Antigens, Surface? It are Antigens on surfaces of cells, including infectious or foreign cells or viruses. They are usually protein-containing groups on cell membranes or walls and may be isolated.
  19. What is Mice, Inbred BALB C? It are
  20. What is Hematopoietic Stem Cells? It are Progenitor cells from which all blood cells derive.
  21. What is Bone Marrow Cells? It are Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells.
  22. What is Luminescent Proteins? It are Proteins which are involved in the phenomenon of light emission in living systems. Included are the “enzymatic” and “non-enzymatic” types of system with or without the presence of oxygen or co-factors.
  23. What is Cell Survival? It are The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.
  24. What is Antigens, CD34? It are Glycoproteins found on immature hematopoietic cells and endothelial cells. They are the only molecules to date whose expression within the blood system is restricted to a small number of progenitor cells in the bone marrow.
  25. What is Membrane Glycoproteins? It are Glycoproteins found on the membrane or surface of cells.
  26. What is Lymphocyte Activation? It are Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.
  27. What is Fluorescent Antibody Technique? It are Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.
  28. What is Antigens, Thy-1? It are A group of differentiation surface antigens, among the first to be discovered on thymocytes and T-lymphocytes. Originally identified in the mouse, they are also found in other species including humans, and are expressed on brain neurons and other cells.
  29. What is Blotting, Western? It are Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.
  30. What is Cell Cycle? It are The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.
  31. What is Antigens, CD45? It are High-molecular weight glycoproteins uniquely expressed on the surface of LEUKOCYTES and their hemopoietic progenitors. They contain a cytoplasmic protein tyrosine phosphatase activity which plays a role in intracellular signaling from the CELL SURFACE RECEPTORS. The CD45 antigens occur as multiple isoforms that result from alternative mRNA splicing and differential usage of three exons.
  32. What is Gene Expression? It are The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.
  33. What is Integrin alpha6? It are An integrin alpha subunit that primarily associates with INTEGRIN BETA1 or INTEGRIN BETA4 to form laminin-binding heterodimers. Integrin alpha6 has two alternatively spliced isoforms
  34. What is Cell Culture Techniques? It are Methods for maintaining or growing CELLS in vitro.
  35. What is Side-Population Cells? It are A group of cells identified on FLOW CYTOMETRY profiles as distinct from the main group of cells by their ability to extrude the fluorescent dye Hoechst 33342, often a characteristic property of less differentiated progenitor and STEM CELLS.
  36. What is Spleen? It are An encapsulated lymphatic organ through which venous blood filters.
  37. What is Tumor Cells, Cultured? It are Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.
  38. What is CD4-Positive T-Lymphocytes? It are A critical subpopulation of T-lymphocytes involved in the induction of most immunological functions. The HIV virus has selective tropism for the T4 cell which expresses the CD4 phenotypic marker, a receptor for HIV. In fact, the key element in the profound immunosuppression seen in HIV infection is the depletion of this subset of T-lymphocytes.
  39. What is B-Lymphocytes? It are Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.
  40. What is Embryonic Stem Cells? It are Cells derived from the BLASTOCYST INNER CELL MASS which forms before implantation in the uterine wall. They retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.
  41. What is Dendritic Cells? It are Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as SKIN and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process ANTIGENS, and present them to T-CELLS, thereby stimulating CELL-MEDIATED IMMUNITY. They are different from the non-hematopoietic FOLLICULAR DENDRITIC CELLS, which have a similar morphology and immune system function, but with respect to humoral immunity (ANTIBODY PRODUCTION).
  42. What is Monocytes? It are Large, phagocytic mononuclear leukocytes produced in the vertebrate BONE MARROW and released into the BLOOD; contain a large, oval or somewhat indented nucleus surrounded by voluminous cytoplasm and numerous organelles.
  43. What is Microscopy, Fluorescence? It are Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.
  44. What is Coculture Techniques? It are A technique of culturing mixed cell types in vitro to allow their synergistic or antagonistic interactions, such as on CELL DIFFERENTIATION or APOPTOSIS. Coculture can be of different types of cells, tissues, or organs from normal or disease states.
  45. What are Transfection? It are The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.
  46. What are Fluorescent Dyes? It are Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.
  47. What are Cell Division? It are The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.
  48. What are Interferon-gamma? It are The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.
  49. What are Genetic Vectors? It are DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.
  50. What are Enzyme-Linked Immunosorbent Assay? It are An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.
  51. What are Annexin A5? It are A protein of the annexin family isolated from human PLACENTA and other tissues. It inhibits cytosolic PHOSPHOLIPASE A2, and displays anticoagulant activity.
  52. What are Mice, Transgenic? It are Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.
  53. What are Leukocytes, Mononuclear? It are Mature LYMPHOCYTES and MONOCYTES transported by the blood to the body’s extravascular space. They are morphologically distinguishable from mature granulocytic leukocytes by their large, non-lobed nuclei and lack of coarse, heavily stained cytoplasmic granules.
  54. What are Cell Adhesion? It are Adherence of cells to surfaces or to other cells.
  55. What are Cytokines? It are Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.
  56. What are Immunohistochemistry? It are Histochemical localization of immunoreactive substances using labeled antibodies as reagents.
  57. What are Mice, SCID? It are Mice homozygous for the mutant autosomal recessive gene “scid” which is located on the centromeric end of chromosome 16. These mice lack mature, functional lymphocytes and are thus highly susceptible to lethal opportunistic infections if not chronically treated with antibiotics. The lack of B- and T-cell immunity resembles severe combined immunodeficiency (SCID) syndrome in human infants. SCID mice are useful as animal models since they are receptive to implantation of a human immune system producing SCID-human (SCID-hu) hematochimeric mice.
  58. What are Cell Lineage? It are The developmental history of specific differentiated cell types as traced back to the original STEM CELLS in the embryo.
  59. What are Gene Expression Regulation? It are Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.
  60. What are Phenotype? It are The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.
  61. What are Gene Expression Profiling? It are The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.
  62. What are Genes, Reporter? It are Genes whose expression is easily detectable and therefore used to study promoter activity at many positions in a target genome. In recombinant DNA technology, these genes may be attached to a promoter region of interest.
  63. What are Cell Movement? It are The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.
  64. What are Antigens, CD3? It are Complex of at least five membrane-bound polypeptides in mature T-lymphocytes that are non-covalently associated with one another and with the T-cell receptor (RECEPTORS, ANTIGEN, T-CELL). The CD3 complex includes the gamma, delta, epsilon, zeta, and eta chains (subunits). When antigen binds to the T-cell receptor, the CD3 complex transduces the activating signals to the cytoplasm of the T-cell. The CD3 gamma and delta chains (subunits) are separate from and not related to the gamma/delta chains of the T-cell receptor (RECEPTORS, ANTIGEN, T-CELL, GAMMA-DELTA).
  65. What is Signal Transduction? It are The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.
  66. What is Interleukin-3 Receptor alpha Subunit? It are A low affinity interleukin-3 receptor subunit that combines with the CYTOKINE RECEPTOR COMMON BETA SUBUNIT to form a high affinity receptor for INTERLEUKIN-3.
  67. What is Killer Cells, Natural? It are Bone marrow-derived lymphocytes that possess cytotoxic properties, classically directed against transformed and virus-infected cells. Unlike T CELLS; and B CELLS; NK CELLS are not antigen specific. The cytotoxicity of natural killer cells is determined by the collective signaling of an array of inhibitory and stimulatory CELL SURFACE RECEPTORS. A subset of T-LYMPHOCYTES referred to as NATURAL KILLER T CELLS shares some of the properties of this cell type.
  68. What is Antigens, Differentiation? It are Antigens expressed primarily on the membranes of living cells during sequential stages of maturation and differentiation. As immunologic markers they have high organ and tissue specificity and are useful as probes in studies of normal cell development as well as neoplastic transformation.
  69. What are Neoplastic Stem Cells? It are Highly proliferative, self-renewing, and colony-forming stem cells which give rise to NEOPLASMS.
  70. What are Fluorescein-5-isothiocyanate? It are Fluorescent probe capable of being conjugated to tissue and proteins. It is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.
  71. What are Time Factors? It are Elements of limited time intervals, contributing to particular results or situations.
  72. What are Polymerase Chain Reaction? It are In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.
  73. What are Endothelial Cells? It are Highly specialized EPITHELIAL CELLS that line the HEART; BLOOD VESSELS; and lymph vessels, forming the ENDOTHELIUM. They are polygonal in shape and joined together by TIGHT JUNCTIONS. The tight junctions allow for variable permeability to specific macromolecules that are transported across the endothelial layer.
  74. What are Biological Markers? It are Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.
  75. What are Microscopy, Confocal? It are A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.
  76. What are Macrophages? It are The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)
  77. What are Cell Membrane? It are The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.
  78. What are Membrane Proteins? It are Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.
  79. What are Colony-Forming Units Assay? It are A cytologic technique for measuring the functional capacity of stem cells by assaying their activity.
  80. What are Molecular Sequence Data? It are Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
  81. What are Lymphocyte Subsets? It are A classification of lymphocytes based on structurally or functionally different populations of cells.
  82. What are Clone Cells? It are A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed)
  83. What are Antibodies? It are Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).
  84. What are Oligonucleotide Array Sequence Analysis? It are Hybridization of a nucleic acid sample to a very large set of OLIGONUCLEOTIDE PROBES, which have been attached individually in columns and rows to a solid support, to determine a BASE SEQUENCE, or to detect variations in a gene sequence, GENE EXPRESSION, or for GENE MAPPING.
  85. What are Antineoplastic Agents? It are Substances that inhibit or prevent the proliferation of NEOPLASMS.
  86. What are Tumor Necrosis Factor-alpha? It are Serum glycoprotein produced by activated MACROPHAGES and other mammalian MONONUCLEAR LEUKOCYTES. It has necrotizing activity against tumor cell lines and increases ability to reject tumor transplants. Also known as TNF-alpha, it is only 30% homologous to TNF-beta (LYMPHOTOXIN), but they share TNF RECEPTORS.
  87. What are Antigens, CD14? It are Glycolipid-anchored membrane glycoproteins expressed on cells of the myelomonocyte lineage including monocytes, macrophages, and some granulocytes. They function as receptors for the complex of lipopolysaccharide (LPS) and LPS-binding protein.
  88. What are Genetic Therapy? It are Techniques and strategies which include the use of coding sequences and other conventional or radical means to transform or modify cells for the purpose of treating or reversing disease conditions.
  89. What are Epithelial Cells? It are Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.
  90. What are Down-Regulation? It are A negative regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.
  91. What are Cell Count? It are The number of CELLS of a specific kind, usually measured per unit volume or area of sample.
  92. What are Recombinant Proteins? It are Proteins prepared by recombinant DNA technology.
  93. What are Fibroblasts? It are Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.
  94. What are Recombinant Fusion Proteins? It are Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes.
  95. What are Endothelium, Vascular? It are Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.
  96. What are Up-Regulation? It are A positive regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.
  97. What are Neural Stem Cells? It are Self-renewing cells that generate the main phenotypes of the nervous system in both the embryo and adult. Neural stem cells are precursors to both NEURONS and NEUROGLIA.
  98. What are HLA-DR Antigens? It are A subclass of HLA-D antigens that consist of alpha and beta chains. The inheritance of HLA-DR antigens differs from that of the HLA-DQ ANTIGENS and HLA-DP ANTIGENS.
  99. What are T-Lymphocyte Subsets? It are A classification of T-lymphocytes, especially into helper/inducer, suppressor/effector, and cytotoxic subsets, based on structurally or functionally different populations of cells.
  100. What are Binding Sites, Antibody? It are Local surface sites on antibodies which react with antigen determinant sites on antigens (EPITOPES.) They are formed from parts of the variable regions of FAB FRAGMENTS.
  101. What are Antigens, Ly? It are A group of lymphocyte surface antigens located on mouse LYMPHOCYTES. Specific Ly antigens are useful markers for distinguishing subpopulations of lymphocytes.
  102. What are Antibody Specificity? It are The property of antibodies which enables them to react with some ANTIGENIC DETERMINANTS and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site.
  103. What are Lymphocytes? It are White blood cells formed in the body’s lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.
  104. What are Fas Ligand Protein? It are A transmembrane protein belonging to the tumor necrosis factor superfamily that was originally discovered on cells of the lymphoid-myeloid lineage, including activated T-LYMPHOCYTES and NATURAL KILLER CELLS. It plays an important role in immune homeostasis and cell-mediated toxicity by binding to the FAS RECEPTOR and triggering APOPTOSIS.
  105. What are Transplantation, Heterologous? It are Transplantation between animals of different species.
  106. What are Dose-Response Relationship, Drug? It are The relationship between the dose of an administered drug and the response of the organism to the drug.
  107. What are Antigens, CD80? It are A costimulatory ligand expressed by ANTIGEN-PRESENTING CELLS that binds to CTLA-4 ANTIGEN with high specificity and to CD28 ANTIGEN with low specificity. The interaction of CD80 with CD28 ANTIGEN provides a costimulatory signal to T-LYMPHOCYTES, while its interaction with CTLA-4 ANTIGEN may play a role in inducing PERIPHERAL TOLERANCE.
  108. What are Staining and Labeling? It are The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.
  109. What are Real-Time Polymerase Chain Reaction? It are Methods used for detecting the amplified DNA products from the polymerase chain reaction as they accumulate instead of at the end of the reaction.
  110. What are RNA, Small Interfering? It are Small double-stranded, non-protein coding RNAs (21-31 nucleotides) involved in GENE SILENCING functions, especially RNA INTERFERENCE (RNAi). Endogenously, siRNAs are generated from dsRNAs (RNA, DOUBLE-STRANDED) by the same ribonuclease, Dicer, that generates miRNAs (MICRORNAS). The perfect match of the siRNAs’ antisense strand to their target RNAs mediates RNAi by siRNA-guided RNA cleavage. siRNAs fall into different classes including trans-acting siRNA (tasiRNA), repeat-associated RNA (rasiRNA), small-scan RNA (scnRNA), and Piwi protein-interacting RNA (piRNA) and have different specific gene silencing functions.
  111. What are Antigens, CD4? It are 55-kDa antigens found on HELPER-INDUCER T-LYMPHOCYTES and on a variety of other immune cell types. CD4 antigens are members of the immunoglobulin supergene family and are implicated as associative recognition elements in MAJOR HISTOCOMPATIBILITY COMPLEX class II-restricted immune responses. On T-lymphocytes they define the helper/inducer subset. CD4 antigens also serve as INTERLEUKIN-15 receptors and bind to the HIV receptors, binding directly to the HIV ENVELOPE PROTEIN GP120.
  112. What are Amino Acid Sequence? It are The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
  113. What are K562 Cells? It are An ERYTHROLEUKEMIA cell line derived from a CHRONIC MYELOID LEUKEMIA patient in BLAST CRISIS.
  114. What are Antigens, CD24? It are A cell adhesion protein that was originally identified as a heat stable antigen in mice. It is involved in METASTASIS and is highly expressed in many NEOPLASMS.
  115. What are Mesenchymal Stromal Cells? It are Bone-marrow-derived, non-hematopoietic cells that support HEMATOPOETIC STEM CELLS. They have also been isolated from other organs and tissues such as UMBILICAL CORD BLOOD, umbilical vein subendothelium, and WHARTON JELLY. These cells are considered to be a source of multipotent stem cells because they include subpopulations of mesenchymal stem cells.
  116. What are T-Lymphocytes, Regulatory? It are CD4-positive T cells that inhibit immunopathology or autoimmune disease in vivo. They inhibit the immune response by influencing the activity of other cell types. Regulatory T-cells include naturally occurring CD4+CD25+ cells, IL-10 secreting Tr1 cells, and Th3 cells.
  117. What are Bone Marrow? It are The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.
  118. What are CD8-Positive T-Lymphocytes? It are A critical subpopulation of regulatory T-lymphocytes involved in MHC Class I-restricted interactions. They include both cytotoxic T-lymphocytes (T-LYMPHOCYTES, CYTOTOXIC) and CD8+ suppressor T-lymphocytes.
  119. What are CHO Cells? It are CELL LINE derived from the ovary of the Chinese hamster, Cricetulus griseus (CRICETULUS). The species is a favorite for cytogenetic studies because of its small chromosome number. The cell line has provided model systems for the study of genetic alterations in cultured mammalian cells.
  120. What are Cell Adhesion Molecules? It are Surface ligands, usually glycoproteins, that mediate cell-to-cell adhesion. Their functions include the assembly and interconnection of various vertebrate systems, as well as maintenance of tissue integration,