Time-cost analysis of a quantum key distribution system clocked at 100 MHz.

We describe the realization of a quantum key distribution (QKD) system clocked at 100 MHz. The system includes classical postprocessing implemented via software, and is operated over a 12 km standard telecommunication dark fiber in a real-world environment. A time-cost analysis of the sifted, error-corrected, and secret key rates relative to the raw key rate is presented, and the scalability of our implementation with respect to higher secret key rates is discussed.

SEMP1, a senescence-associated cDNA isolated from human mammary epithelial cells, is a member of an epithelial membrane protein superfamily.

We have cloned a human cDNA, SEMP1 (senescence-associated epithelial membrane protein 1), using differential display (DD) of mRNA. We compared mRNA expression profiles between cultured normal senescent human mammary epithelial cells (HMECs) and proliferating, early passage HMECs. From the amino acid sequence of the open reading frame (ORF) of the cDNA, we infer that the protein belongs to a family of membrane-associated, epithelial cell-specific proteins. The translation product has 91% identity to a mouse protein, claudin-1, a tight junction (TJ)-associated protein. SEMP1 mRNA is expressed in human tissues, including adult and fetal liver, pancreas, placenta, adrenals, prostate and ovary but at low or undetectable levels in a number of human breast cancer cell lines. SEMP1 is a member of a superfamily of epithelial membrane proteins (EMPs), which may have multiple potential functions, including maintenance and regulation of cell polarity and permeability, perhaps through mechanisms involving tight junctions.

A thymic stromal cell line supports in vitro development of surface IgM+ B cells and produces a novel growth factor affecting B and T lineage cells.

A thymic stromal cell line with a medullary phenotype (Z210R.1) supported the differentiation of surface IgM+ B cells when cocultured with fetal liver cells in vitro. Conditioned medium (CM) from this cell line supported the long-term growth of a B cell line (NAG8/7) isolated from cocultures and enhanced the proliferation of unfractionated thymocytes to suboptimal concentrations of anti-CD3 antibodies in vitro. Biological assays of the CM detected interleukin-7 (IL-7) but not IL-1, IL-2, IL-3, IL-4, IL-6, Steel factor (SCF), leukemia inhibitory factor (LIF), or macrophage or granulocyte colony-stimulating factors (M-CSF or G-CSF). The failure of recombinant IL-7 to maintain the long-term growth of NAG8/7 cells and the inability of anti-IL-7 antibodies to significantly affect the response of either NAG8/7 cells or thymocytes to CM suggested the presence of one or more other cytokines in the CM. Analysis of concentrated CM fractionated by anion exchange chromatography revealed a single peak of activity in the NAG8/7 assay with an elution profile that was distinct from IL-7. Two peaks of activity were detected in the thymocyte response to anti-CD3 antibodies; one corresponded to IL-7 and the other corresponded to the same fractions that stimulated NAG8/7 cells. The second peak of thymocyte stimulatory activity could not be inhibited by neutralizing anti-IL-7 antibodies. In addition to producing a cytokine with unique properties, this thymic stromal cell exhibits a functional homology to bone marrow or fetal liver stromal cells not previously appreciated.

Medullary thymic epithelium expresses a ligand for CTLA4 in situ and in vitro.

A fusion protein consisting of the extracellular domain of CTLA4 and an Ig C gamma 1 chain (CTLA4-Ig) was used to examine the distribution of the ligands for CTLA4 within the murine thymus and to characterize the nature of these ligands. Two-color immunofluorescence of thymus tissue revealed binding of the fusion protein to medullary thymic epithelial cells and dendritic cells within the corticomedullary and medullary areas of the thymus. Medullary cells binding the fusion protein also expressed MHC class II products and ICAM-1. Thymus tissue sections treated with cross-linking fixatives, such as glutaraldehyde, paraformaldehyde, or 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide no longer bound the CTLA4 fusion protein, indicating that binding was very sensitive to the tertiary structure of the tissue ligand. The ability of thymic tissue to bind the fusion protein was developmentally regulated. At day 14 of gestation, only scattered single cells were labeled. Clusters of labeled cells, which were detected by day 16 of gestation, increased in frequency with advancing gestational age. Consistent with the in situ labeling studies, CTLA4-Ig also labeled several thymic epithelial cell lines previously shown to have a medullary phenotype. Polymerase chain reaction analysis of mRNA extracted from these cells indicated they contained mRNA for B7, a known counter receptor for CTLA4 and CD28. Immunoprecipitation of 125I-labeled thymic epithelial cells with the CTLA4-Ig detected a M(r) 65,000 to 70,000 species under reducing conditions, consistent with previous studies of B7. These data suggest that the ligand for CTLA4 expressed by thymic epithelial cells in vitro is B7 and that the expression of this ligand in situ is largely restricted to the medullary compartment and is associated with epithelial cells and dendritic cells.

A novel cytokine-responsive cell surface glycoprotein defines a subset of medullary thymic epithelium in situ.

A hamster mAb (10.1.1), raised against long term cultures of uncloned thymic stromal cells, selectively labeled a subpopulation of medullary stromal cells in situ. By ultrastructural and phenotypic criteria, the stromal cells labeled by this mAb were judged to be epithelial. Although some of the 10.1.1+ epithelial cells were reticular, others were globular and some were associated with structures resembling Hassal's bodies. Ultrastructural immunohistochemistry suggested that 10.1.1 labeling of some of the epithelial cells was preferentially associated at areas of epithelial cell contact with adjacent thymocytes. Reactivity of thymic stromal cells with this antibody was developmentally regulated. A few scattered 10.1.1+ cells were observed at day 14 of gestation, and there were progressive increases in both the extent and intensity of 10.1.1 labeling evident through birth. One thymic stromal cell line, Z210.1, exhibited low levels of constitutive reactivity with this antibody. Exposure to IL-1 resulted in enhanced 10.1.1 reactivity of this cell line, with little, if any, additional response to TNF-alpha or IFN-gamma. Under the same conditions, ICAM-1 expression by this cell line was elevated in response to IL-1, TNF-alpha, or INF-gamma. Immunoprecipitation of detergent lysates prepared from Z210.1.7 cells exposed to IL-1 24 h before cell surface iodination identified a cell surface protein with a molecular mass of about 92 kDa under nonreducing conditions and about 95 kDa under reducing conditions. Digestion of 10.1.1 immunoprecipitates with N-glyconase resulted in a small (5 kDa) reduction in molecular mass. The molecule recognized by the 10.1.1 mAb was distinct from ICAM-1, which possessed a molecular mass of 100 kDa (nonreduced) and 110 kDa (reduced), and also displayed a smaller N-glyconase-resistant molecular mass (65 to 85 kDa).

Characterization of an antigenic determinant preferentially expressed by type I epithelial cells in the murine thymus.

A hamster monoclonal antibody (MAb), designated 8.1.1, was raised against murine thymic stromal cell lines and was found to react with cell surface molecules expressed by a morphologically distinct population of epithelial cells of the murine thymus comprising the subcapsular environment, cells investing vascular structures throughout the thymus, and some of the cellular elements in the medulla. The epithelial nature of the labeled cells was confirmed with immunoelectron microscopy. Reactivity with MAb 8.1.1 was associated with thymic epithelial cells in contact with basal laminae. Ontological studies of thymic tissue demonstrated that the epitope recognized by this MAb was expressed before Day 14 of gestation, although the restricted subcapsular and medullar expression of 8.1.1 was not apparent until sometime after birth. MAb 8.1.1 also reacted with a number of extra-thymic tissues, including lamina propria of gut, glomeruli and tubules in the kidney, mesothelia covering a number of organs, and the dermis and epidermis of skin. Within the epidermis, reactivity of MAb 8.1.1 was largely restricted to basal epithelial cells. Immunochemical analysis of 8.1.1 reactivity with detergent-soluble extracts of thymic stromal cell lines and thymus tissue indicated that detergent-soluble extracts of thymic stromal cell lines and thymus tissue indicated that the epitope recognized by this MAb was associated with a glycoprotein bearing terminal N-acetylglucosamine residues and possessing an Mr of approximately 36-38 KD under reducing or non-reducing conditions.

Epithelial heterogeneity in the murine thymus: a cell surface glycoprotein expressed by subcapsular and medullary epithelium.

A monoclonal antibody (MAb), G8.8, was raised against glycoconjugates isolated from a cloned line of murine medullary thymic epithelial cells. Flow cytometric analysis of the reactivity of this MAb with cultured thymic epithelium demonstrated that the ligand was expressed on the cell surface. Immunohistochemical examination of normal murine thymus revealed labeling of cells in the subcapsular and medullary areas. Immunoelectron microscopy revealed surface labeling restricted to cells possessing ultrastructural features of epithelium (desmosomes, tonofilaments, and cytoplasmic cysts). During thymic ontogeny, G8.8+ cells predominated in fetal development at the earliest time point examined (Day 14 of gestation). There was an expansion of the cortical epithelial component so that by Day 18 cortical and medullary compartments could be clearly distinguished. Immunoprecipitation of radioiodinated thymic stroma with MAb G8.8 detected a molecule with an apparent Mr of approximately 38 KD under non-reducing conditions. When reduced, the apparent Mr was slightly increased (42 KD). This MAb also exhibited reactivity with gut and epidermal epithelium and some tubular epithelium in the kidney, but did not react with epithelial parenchymal cells of the liver.

Distribution of thymocytes expressing gamma delta receptors in the murine thymus during development.

We have examined the appearance of thymocytes expressing gamma delta TCR within the developing thymus by using immunohistochemical techniques and flow cytometry in conjunction with the mAb 3A10, which recognizes a determinant associated with the constant region of the delta-chain. gamma delta+ Cells were first detected at day 16 of gestation, attained maximal levels at day 17 of gestation, and declined thereafter. By using the Ulex europeus agglutinin to identify medullary epithelial cells in situ, we observed a striking colocalization of gamma delta+ thymocytes and U. europeus agglutinin-positive medullary epithelial cells during late fetal and neonatal periods of development. In the thymuses of adult mice, gamma delta+ thymocytes were scattered throughout cortical and medullary areas of the thymus and most concentrated in the subcapsular areas of the thymus. Ultrastructural immunohistochemistry confirmed the close association between medullary thymic epithelial cells and gamma delta+ thymocytes in the neonatal thymus and also showed that some TCR-gamma delta molecules were patched to areas of contact with medullary epithelial cells. In contrast to the cellular distribution of either CD3 molecules or the TCR-alpha beta, where extensive intracellular labeling of thymocytes has been observed, cytoplasmic accumulation of delta-chain was not detected.

Medullary epithelial cell lines from murine thymus constitutively secrete IL-1 and hematopoietic growth factors and express class II antigens in response to recombinant interferon-gamma.

In this report, we describe the generation of two cloned epithelial cell lines, TE-71 and TE-75, from murine thymus. These cell lines resemble medullary thymic epithelium by a number of criteria, including reactivity with the monoclonal antibodies A2B5 and ER-TR5, the fucose-specific lectin derived from Ulex europeus, and the expression of keratins normally expressed by medullary thymic epithelial cells in situ. Constitutive Class II antigen expression by these cells is not detectable at the light or electron microscopic level or with flow cytometry. Following exposure to recombinant interferon-gamma or supernatants from mitogen-stimulated spleen cells, expression of Class II antigens by these thymic epithelial cell lines is increased, although less than the levels expressed by spleen cells. Medium conditioned by TE-71 and TE-75 cells exhibited colony-stimulating activity for bone marrow cells. In addition, TE-71-conditioned medium exhibited IL-1-like activity which could be neutralized with anti-IL-1 antibodies.