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1.
Direct identification of the murine IL-2 receptor p55-p75 heterodimer in the absence of IL-2 总被引:7,自引:0,他引:7
The proteins cross-linked to the IL-2R p55 subunit were biochemically compared in distinct cell populations that varied in their capacity to express high affinity IL-2R. We directly cross-linked p75 to p55 in the absence of IL-2 for the cell populations that bear only high affinity IL-2R. Furthermore, although no endogenous IL-2 production was detected, p75 was readily cross-linked to p55 for EL4J-3.4, a p55 transfectant of EL4 that bears high affinity IL-2R. These results strongly suggest that high affinity IL-2R exist as a preformed heterodimer of p55 and p75 which do not require IL-2 for their association. Furthermore, cross-linking of three other proteins of apparent Mr of 100,000, 135,000, and 180,000 to p55 was also seen, raising the possibility of a more complex subunit composition for the IL-2R. 相似文献
2.
G Steiner E Tschachler M Tani T R Malek E M Shevach W Holter W Knapp K Wolff G Stingl 《Journal of immunology (Baltimore, Md. : 1950)》1986,137(1):155-159
Rat monoclonal antibodies 3C7 and 7D4 detect two distinct functional regions of the murine interleukin 2 (IL 2) receptor. When studying the emergence kinetics of IL 2 receptors in mixed epidermal cell (EC)-lymphocyte cultures by using 3C7 and 7D4 in an indirect immunofluorescence assay, we regularly encountered a distinctive membrane fluorescence not only on lymphocytes, but also on a subpopulation of cells exhibiting a dendritic morphology. Reasoning that these 3C7/7D4-reactive dendritic cells might represent a subpopulation of epidermal dendritic cells, we studied mouse EC for the presence of 3C7/7D4- reactive cells. Although 3C7/7D4 reactivity was never detected on freshly isolated EC or on epidermal sheets, a small number of 3C7/7D4+ cells was encountered after 24 to 48 hr of culture. These cells exhibited a dendritic shape, expressed Ia antigens, lacked Thy-1 antigens, and displayed the ultrastructural features of Langerhans cells (LC) with the notable exception of Birbeck granules. Although after 24 hr, only 20% of Ia+ EC were 3C7/7D4+, the vast majority of LC displayed 3C7/7D4 binding sites after 4 to 5 days of culture. Preincubation of cultured LC-enriched EC with recombinant human IL 2 prevented subsequent 3C7-but not 7D4-binding to these cells. Western blot analysis of 7D4-reactive material of detergent extracts from LC-enriched EC revealed three bands in the same m.w. range as reported for CTLL cells. These results demonstrate that cultured LC express IL 2 receptors and may bear important implications for a better understanding of growth regulation, differentiation, and immunologic functions of LC. 相似文献
3.
Regulation of B lymphocyte responses to IL-4 and IFN-gamma by activation through Ly-6A/E molecules 总被引:1,自引:0,他引:1
The Ly-6 family of cell surface molecules has previously been shown to participate in T cell activation. We show that Ly-6A/E proteins also modulated the response of normal B lymphocytes in three separate in vitro assays. First, unfractionated or small resting B cells proliferated when cultured with IFN-gamma, IL-4, and an anti-Ly-6A/E mAb. Second, this anti-Ly-6A/E mAb restored B cell proliferation responses that were inhibited when coculturing the B cells in IFN-gamma, IL-4, and anti-IgM. Third, anti-Ly-6A/E specifically up-regulated the cell surface expression of its own Ag, and this response was dependent upon co-stimulation with IFN-gamma. Mixing of T and B cells in culture suggested that T cells did not contribute substantially to the B cell proliferative response. Moreover, up-regulation of Ly-6A/E was observed for one B cell lymphoma, WEHI-231. Therefore, it appeared that modulation of B cell function by anti-Ly-6A/E was due to a direct effect of the mAb binding to the B cells. Taken together, these data suggest Ly-6A/E proteins are functional on B cells and may play a regulatory role in B cell activation. 相似文献
4.
E K Codias J E Rutter T J Fleming T R Malek 《Journal of immunology (Baltimore, Md. : 1950)》1990,145(5):1407-1414
Ly-6A/E molecules are expressed on the surface of T cells and have been shown to function in activation by the capacity of anti-Ly-6A/E mAb to induce T cell hybridomas or normal T cells to produce IL-2. Recent evidence suggests that activation through Ly-6A/E may be linked to the TCR signaling pathway. To further investigate the relationship between Ly-6- and TCR-induced T cell activation, we have examined whether an anti-Ly-6A/E mAb (D7) modulates TCR signaling in vitro. We now report that mAb D7 specifically inhibited IL-2 production by T cells also activated through TCR. Such inhibition was noted for normal T cells stimulated by soluble anti-CD3 or alloantigen and for T hybridomas stimulated by soluble anti-CD3. The ability of D7 to inhibit IL-2 production by T hybridomas was dependent on the nature of the TCR activating signal because IL-2 production was not inhibited when T hybridomas were stimulated with Ag or immobilized anti-CD3. Inhibition of IL-2 production by D7 apparently required cross-linking of the mAb because D7 F(ab')2 fragments were not effective for inhibition of IL-2 production. Similar to its ability to enhance anti-Ly-6A/E-induced activation of T and B cells, IFN-gamma enhanced the D7-induced inhibition of IL-2 production by alloantigen-activated normal T cells. These data further support the notion that Ly-6 and TCR signaling pathways are interrelated. 相似文献
5.
Inactivation of the Porphyromonas gingivalis fimA gene blocks periodontal damage in gnotobiotic rats. 总被引:22,自引:1,他引:21 下载免费PDF全文
R Malek J G Fisher A Caleca M Stinson C J van Oss J Y Lee M I Cho R J Genco R T Evans D W Dyer 《Journal of bacteriology》1994,176(4):1052-1059
Fimbrial production by Porphyromonas gingivalis was inactivated by insertion-duplication mutagenesis, using the cloned gene for the P. gingivalis major fimbrial subunit protein, fimA. by several criteria, this insertion mutation rendered P. gingivalis unable to produce fimbrilin or an intact fimbrial structure. A nonfimbriated mutant, DPG3, hemagglutinated sheep erythrocytes normally and was unimpaired in the ability to coaggregate with Streptococcus gordonii G9B. The cell surface hydrophobicity of DPG3 was also unaffected by the loss of fimbriae. However, DPG3 was significantly less able to bind to saliva-coated hydroxyapatite than wild-type P. gingivalis 381. This suggested that P. gingivalis fimbriae are important for adherence of the organism to saliva-coated oral surfaces. Further, DPG3 was significantly less able to cause periodontal bone loss in a gnotobiotic rat model of periodontal disease. These observations are consistent with other data suggesting that P. gingivalis fimbriae play an important role in the pathogenesis of human periodontal disease. 相似文献
6.
Summary The use of molluscivorous fish for biological control of snail intermediate hosts of schistosomiasis is a regularly reappearing theme in the literature on schistosomiasis control. The effectiveness of this control method has not yet been demonstrated, and conclusive field evidence is lacking. In this article the literature on snail control by fish is critically reviewed. Special attention is paid to the cichlid fish Astatoreochromis alluaudi that has been used in well-documented field trials in Kenya and Cameroon. After some small initial success, after a longer period the fish appeared to be ineffective in snail control. Moreover, the fish reproduces at a pace too slow to be of use in large-scale biocontrol trials. Laboratory observations on foraging behaviour and anatomy of the fish give essential cues to explain the failure of the fish in snail control. An observed reduction in the fishes' pharyngeal jaw apparatus, used to crush snails shells, results in a lower profitability of snails. As predicted by a simple foraging model, the prey preference of the fish shifts towards other more profitable prey items, such as benthic and pelagic macrofauna. Although eradication of snails by fish will not be feasible in most cases, the role of natural predators of snails cannot be neglected, and may still be of importance in integrated control efforts. 相似文献
7.
Butler Michael J. Aphale Jayant S. DiZonno Michele A. Krygsman Phyllis Walczyk Eva Malek Lawrence T. 《Journal of industrial microbiology & biotechnology》1994,13(1):24-29
Summary We have investigated the aminopeptidase activities present inStreptomyces lividans strains. The majority of these activities proved to be intracellular with multiple active species. Two aminopeptidase P genes were identified to be responsible for the ability to hydrolyze amino terminal peptide bonds adjacent to proline residues. Two other broad spectrum aminopeptidases were found to display homology at both the DNA and protein levels. One showed significant homology to PepN proteins, particularly around the putative zinc-binding residues which are important for catalysis. The second broad spectrum activity was not analyzed in detail but showed a different spectrum of substrate specificity to that of PepN. 相似文献
8.
Heterogeneity of the 5' terminus of hen ovalbumin messenger ribonucleic acid. 总被引:11,自引:7,他引:4 下载免费PDF全文
The 5'-terminal sequence of hen ovalbumin mRNA was investigated using a novel labeling method. Ovalbumin mRNA was purified by hybridization to complementary DNA coupled to cellulose. The mRNA thus purified was shown to be 97.9% pure by hybridization with plasmid DNA containing sequences to the messengers coding for conalbumin and ovomucoid, the next two most abundant messengers of oviduct. After digestion with RNase T1 and alkaline phosphatase, 5'-terminal capped oligonucleotides were selected by binding to anti-m7G-Sepharose. These were then labeled using RNA ligase and [5'-32P]pCp, separated by two-dimensional gel electrophoresis, and sequenced by partial digestion with base-specific ribonucleases. A nested set of three capped oligonucleotides was identified. Their structures and relative abundances were m7GpppAUACAG, 3% m7GpppACAUACAG, 61+; and m7GpppGUACAUACAG, 36%. 相似文献
9.
Competition between Gs-protein and the synthetic peptide, GSA 379-394, derived from the carboxyl-terminal region of the alpha s-subunit, led to complete inhibition of receptor-mediated adenylate cyclase activation in turkey erythrocyte membranes. Related peptides corresponding to the homologous carboxyl-terminal region of alpha t-, alpha il- or alpha o-subunits did not interfere with beta-receptor-Gs coupling. The direct coupling between Gs and adenylate cyclase was not influenced by any of these peptides. These results emphasize the important role of the carboxyl-terminus of G-protein alpha-subunits for the specific recognition of their corresponding receptors and for signal transduction. 相似文献
10.