1,721,003 research outputs found
Trans-acting element(s) operating across species barriers positively regulate expression of major histocompatibility complex class II genes.
No full textStable integration of mouse DNA into Ia-negative human B-lymphoma cells causes reexpression of the human Ia-positive phenotype.
No full textTranscriptional control of MHC class II gene expression during differentiation from B cells to plasma cells.
No full textA family of trans-acting factors with distinct regulatory functions control expression of MHC class II genes.
No full textThe regulation of expression of MHC class II genes is mainly exerted at the transcription level. Three short and conserved sequences have been identified at the gene promoter region, common to all MHC class II genes, named W, X and Y, where specific trans-acting factors bind, to initiate transcription. We have recently identified a trans-acting factor encoded by the Activator Immune Response genes-1 (AIR-1) locus, whose action is essential to guarantee MHC class II gene transcription, apparently acting on all three regions, although the binding features are still to be defined
Active suppression of major histocompatibility complex class II gene expression during differentiation from B cells to plasma cells.
No full text
Inducible and constitutive MHC class II gene expression. Distinct tissue-specific genetic controls.
No full textB cells express MHC class II Ag in a constitutive fashion, whereas macrophages can do so only after induction by a variety of exogenous stimuli. In this study we describe interspecies somatic cell hybrids between the human B cell Raji and the murine macrophage cell P388 D1. This murine cell line does not express detectable levels of class II mRNA. Phenotypic, molecular, and karyotype analysis of a series of hybrids showed that murine macrophage class II genes can be expressed in a constitutive fashion under the control of the human B cell genome. This event is the consequence of de novo accumulation of class II specific mRNA and thus probably reflects activation of transcription. In certain cases the amount of murine class II Ag expressed on the surface of the hybrid cell was significantly higher than the one observed in the parental macrophage cells after induction with IFN-gamma and was not further modified by treatment with the murine lymphokine. Reversion from a murine class II-positive to class II-negative cell surface phenotype in the hybrids correlated with reduced expression of human markers and more important with segregation of human chromosomes. Interestingly, in this case certain hybrids still expressed detectable levels of murine class II mRNA and increased levels of murine invariant chain mRNA when compared with parental P388 D1 murine macrophage cells. These results indicate that constitutive class II gene expression behaves as a dominant trait in B cell x macrophage somatic cell hybrids. Possible mechanisms responsible of the different control of class II gene expression during cell type differentiation are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
aIr-1, a newly found locus on mouse chromosome 16 encoding a trans-acting activator factor for MHC class II gene expression.
Get PDFRJ 2.2.5 is a human B cell line that has lost the capacity to express MHC class II genes. The human class II-positive phenotype is restored in somatic cell hybrids between RJ 2.2.5 and mouse spleen cells. By karyotype and molecular studies of an informative family of hybrids we have now shown that the reexpression of human class II gene products, as well as the maintenance of the mouse class II-positive phenotype, correlates with the presence of mouse chromosome 16. Thus, the existence on this mouse chromosome of a newly found locus, designated by us aIr-1, that determines a trans-acting activator function for class II gene expression, is established. Possible implications of this finding are discussed
- …
