Search

The embryonic thymus is colonized by the influx of hemopoietic progenitors in waves. To characterize the T cell progeny of the initial colonization waves, we used intravenous adoptive transfer of bone marrow progenitors into congenic embryos. The experiments were performed in birds because intravenous cell infusions can be performed more efficiently in avian than in mammalian embryos. Progenitor cells, which entered the vascularized thymus via interlobular venules in the capsular region and capillaries located at the corticomedullary junction, homed to the outer cortex to begin thymocyte differentiation. The kinetics of differentiation and emigration of the T cell progeny were analyzed for the first three waves of progenitors. Each progenitor wave gave rise to gamma/delta T cells 3 d earlier than alpha/beta T cells. Although the flow of T cell migration from the thymus was uninterrupted, distinct colonization and differentiation kinetics defined three successive waves of gamma/delta and alpha/beta T cells that depart sequentially the thymus en route to the periphery. Each wave of precursors rearranged all three TCR Vgamma gene families, but displayed a variable repertoire. The data indicate a complex pattern of repertoire diversification by the progeny of founder thymocyte progenitors.

A candidate avian CD6 homolog is identified by the S3 monoclonal antibody. The S3 antigen exists in a phosphorylated glycoprotein form of 130 kDa and a nonphosphorylated form of 110 kDa. Removal of phosphate groups and N-linked carbohydrates indicates a 78-kDa protein core. During thymocyte differentiation, the gamma delta T cells do not express S3, whereas mature CD4+ and CD8+ cells of alpha beta lineage acquire S3 antigen. All alpha beta T cells in the blood and spleen express the S3 antigen at relatively high levels. In contrast, only the CD8+ subpopulation of gamma delta T cells in the spleen expresses the antigen and neither alpha beta nor gamma delta T cells in the intestinal epithelium express the S3 antigen. The S3 antigen is also found on embryonic splenocytes with a phenotypic profile characteristic of avian natural killer cells. The biochemical characteristics and this cellular expression pattern imply that the S3 antigen is the chicken CD6 homolog.

To examine the role of T cell subpopulations in an acute graft-versus-host (GVH) reaction, gamma delta T cells and alpha beta T cells expressing one of the two prototypic V beta families were negatively isolated from adult blood samples and injected into allogeneic chick embryos. CD4+ alpha beta T cells expressing either V beta 1 or V beta 2 receptors were equally capable of inducing acute GVH reactions, consistent with the idea that alpha beta T cell alloreactivity is determined by CDR3 variability. By themselves, the gamma delta T cells were incapable of inducing GVH reactions. However, host gamma delta T cells were recruited into the donor alpha beta T cell-initiated lesions, where they were activated and induced to proliferate. The data suggest that gamma delta T cells may play a secondary role in GVH reactions.

A quasi-dynamic traffic assignment model is proposed,in which the traffic demand is time-varying and the queues are time-dependent under the quasi-dynamic condition. The proposed model can estimate simultaneously traffic flows and queues in the network at various time intervals andlor under different traffic conditions, especially when the total traffic demand exceeds the network capacity in the peak period. By carrying queues over from one time interval to the next, the temporary over-loading of the network which characterises peak periods can be allowed for. Steady state conditions are assumed within each time interval, so avoiding difficulties with first-infirst-out (FIFO) in the queuing process. A mathematical programming model, where optimal solution satisfies the user equilibrium condition, is developed for the timevarying traffic assignment with time-dependent queues. Numerical examples are given to illustrate its applications.

This review summarizes our current view of gamma delta and alpha beta T cell development in the chicken. In it we emphasize the functional interplay between the gamma delta and alpha beta T cell subpopulations.

T-cell receptor (TCR) alpha-chain (TCR alpha) and beta-chain (TCR beta) genes are well characterized in mammals, while only TCR beta genes have been identified in other vertebrates. To identify avian TCR alpha genes, we used monoclonal anti-CD3 antibodies to isolate chicken TCR alpha for peptide sequence analysis. Degenerate oligonucleotide probes were then used to isolate a candidate TCR alpha cDNA clone that hybridized with a 1.7-kb mRNA species present only in alpha beta T cells and in tissues populated by these cells. Southern blot analysis revealed gene rearrangement in thymocytes and alpha beta T-cell lines. The TCR alpha cDNA candidate encoded an open reading frame of 275 amino acids, the predicted variable (V)-, joining (J)-, and constant (C)-region amino acid sequences of which shared approximately 40%, 60%, and 25% homology with corresponding mammalian sequences. A single C alpha gene and approximately 25 V alpha genes were identified by using region-specific probes. The V alpha cDNA probe isolated from a V beta 1+ cell line reacted with transcripts from one of five V beta 2+ cell lines, suggesting shared use of V alpha genes by V beta 1+ and V beta 2+ T cells and the existence of other V alpha gene families. A genomic V alpha sequence was flanked by classical recombination signal sequences but, unlike previously defined V genes, the leader and V alpha region were encoded by a single exon. The data indicate evolutionary conservation of the basic TCR alpha gene structure in birds and mammals.

The Protein and Metabolite Analysis Facility at the University of Texas at Austin is a joint effort of the College of Pharmacy, Center for Research on Environmental Disease (CRED), and the Institute for Cellular and Molecular Biology (ICMB). Services and collaborative research are offered for the detection, characterization and quantification of biomolecules. The Facility's goals are to provide sensitive protein identification and modification analyses, to provide custom peptide syntheses, to offer services for the identification and quantification of metabolites, nutrients and xenobiotics, to implement novel analytical methods, to improve the sensitivity of existing analyses, to provide consultation on the selection and implementation of analytical methods, to offer training in the usage and applications of the instrumentation, and to provide technical expertise in support of individual research goals. The ICMB portion of the Core contains an ABI Procise 492 cLC protein sequencer, a Protein Technologies Inc. Symphony peptide synthesizer, two Bio-rad Duoflows and a GE Heathcare AKTA protein purification systems, two Beckman System Gold HPLC systems, a Berthold Technologies Mithras luminescence and fluorescence detector, an Invitrogen gel electrophoresis set-up, an Art Robbins Instruments Phoenix crystallography robot and a LC-MALDI-TOF/TOF (an ABI 4700 with a LC Packings Ultimate Nano-LC system with a Probot spotting robot). In the College of Pharmacy, the Core has an Applied Biosystems 4000 Q-trap LC MS/MS system with ESI, APCI and nanospray sources coupled with a Shimadzu LC-20AD HPLC system, ThermoFinnigan LCQ ion trap mass spectrometer with ESI, APCI and microspray interfaces combined with a Michrom Magic 2002 HPLC system, a ThermoFinnigan Trace MS GC-quadropole with EI positive, negative CI and selected ion monitoring (SIM), an ABI Voyager-DE Pro MALDI-TOF and a Bio-rad Bioplex 200 fluorescent microbead array system.

Thymocyte development was monitored in an embryonic thymus organ culture system to establish a model in the chicken in which the functional nature of the thymic microenvironment could be assessed. Thymus lobes were removed from 10-day-old embryos and cultured for 2-10 days. Cell yield increased to a maximum in 4-8 days of culture with a corresponding decrease in average cell size. An initial thymocyte population of predominantly CD3-CD4-CD8- cells gave rise to all CD3/CD4/CD8-defined subpopulations in vitro, maintaining high levels of CD3-CD4-CD8+ and CD3+CD4-CD8+ cells and a low representation of CD3-CD4+CD8-, CD3+CD4+CD8-, CD3-CD4+CD8+ and CD3+CD4+CD8+ thymocytes. This is the first observation of a CD3-CD4+CD8- population in the chicken. Developmental kinetics of CD3+ cells were similar to that in the embryo, suggesting that the in vitro environment is sufficient to promote and maintain thymocyte maturation. Thymocytes of both the gamma delta and alpha beta T cell receptor (TcR) lineages developed in that order, confirming in ovo data and the lineage potential of the first wave of thymocyte precursors. One unusual finding was a relative accumulation of gamma delta TcR+ thymocytes in culture, incorporating all CD4/CD8 subsets, including a previously undetected population, CD4+CD8-. This may indicate a favorable developmental environment or simply a lack of normal cellular emigration. A detailed comparison with T cell development in the embryo demonstrated that the chicken thymus organ culture system reflects thymic events in ovo during a limited time period and thus should prove useful in the identification of functionally relevant thymic molecules.

In a study of T cell ontogeny using monoclonal antibodies specific for chicken T cell receptors (TcR) and associated cell surface molecules, we found a subset of lymphocytes that express cytoplasmic CD3 epitopes in the absence of cell surface CD3/TcR complexes. Approximately half of these cells, which were present in the spleen, bursa and intestine of young chick embryos, expressed surface CD8. None expressed CD4, TcR 1 (gamma/delta), TcR 2 (alpha/beta) or TcR 3 (a third CD3-associated heterodimer in the chicken). These cytoplasmic CD3+CD8 +/- cells, tentatively named TcR 0 cells to denote their lack of surface TcR, appeared first in the spleen of 8-day embryos, 4 days before TcR expression begins in the thymus, and reached a peak frequency of approximately 10% of the splenic cell in 14-day embryos. The TcR 0 cells were also present in adult birds, where they comprised only about 1% of the CD3+ spleen cells and approximately 40% of the lymphocytes in the intestinal epithelium. We conclude that the avian TcR 0 cells represent a thymus-independent lineage of lymphocytes which, like natural killer cells in mammals, may play an important role in body defense.

A member of the family of β2-microglobulin (β2m)-associated cell surface glycoproteins was identified by the CB3 monoclonal antibody. The Mr 50 000 heavy chain of the CB3 antigen differs from conventional class I heavy chains (Mr 45 000) in the extent of glycosylation, charge, and peptide composition. Because of its selective expression on avian B cells and its similarity to mammalian class I-like molecules, we speculate that the CB3 antigen may play a role in T- and B-cell interactions. rommental stimuli is to prepare monoclonal antibodies against bursal cell surface antigens. Using this strategy we have identified several proteins that are expressed on the surface of bursal B cells (Chen and Cooper 1987). In the present study we characterize CB3, a class I-like molecule associated with β2-microglobulin (β2m) on the surface of both bursal and peripheral B cells.

Metadata only record Pour mieux consolider les acquis consensuels pour la gestion alternative des conflits, il nous paraît essentiel de maîtriser un certain nombre de facteurs ayant trait au "partage" des gommeraies entre autres: Available in SANREM office, FS

The effect of steroid treatment on the thymic output of T cells was examined in an avian model. Recent thymic emigrants in chickens transiently express the chicken T cell Ag 1 thymocyte marker, and thymic function can be monitored indirectly by measuring the levels of TCR gene rearrangement excision circles in peripheral T cells. Both parameters were used to show that intensive steroid treatment induces thymic involution and a profound reduction in the supply of naive T cells to the periphery. Conversely, resident T cells in the peripheral lymphocyte pool were relatively spared. Thymopoiesis immediately recovered following cessation of steroid treatment, concurrent with restoration of the thymic output of newly formed T cells. Repopulation of the peripheral T cell pool recapitulated the ontogenetic pattern of γδ T cell replenishment before αβ T cell reseeding, thereby indicating the complete recovery of thymic function after a course of steroid treatment.

The avian B cell differentiation Ag chB1 is a membrane glycoprotein relative of the mammalian B cell differentiation Ag CD72. Unlike CD72, this C-type lectin is expressed in relatively high levels on immature B cells in the bursa of Fabricius and is down-regulated on mature B cells in the periphery. An immunoreceptor tyrosine-based inhibitory motif in the chB1 cytoplasmic tail suggests a potential regulatory role in intrabursal B cell development. To gain further insight into the selective expression and function of chB1, we determined the genomic organization of chB1 and examined the mechanism of its transcriptional regulation. The 8-exon chB1 gene proved to have very similar organization to that of mouse CD72, further supporting the idea that chB1 is a CD72 relative. As for mouse CD72, the chB1 promoter region lacks a TATA box but contains a conserved initiator element. The 131-bp region (−161 to −30) proximal to the transcriptional start site, which contains a potential early B cell factor binding site, is essential for the B lineage stage-specific transcription of chB1, whereas PU.1 and B cell-specific activator protein/Pax5 have been shown to play important roles in CD72 promoter activity and cell-type specificity. This analysis suggests that differences in transcriptional regulation of these phylogenetically related genes may determine the differences in expression pattern and, therefore, the function of avian chB1 and mammalian CD72 during B cell development.