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排序方式: 共有118条查询结果,搜索用时 15 毫秒
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Induction of cytosolic calcium flux by CD20 is dependent upon B Cell antigen receptor signaling 总被引:2,自引:0,他引:2
Walshe CA Beers SA French RR Chan CH Johnson PW Packham GK Glennie MJ Cragg MS 《The Journal of biological chemistry》2008,283(25):16971-16984
The anti-CD20 monoclonal antibody (mAb) rituximab is now routinely used for the treatment of non-Hodgkins lymphoma and is being examined in a wide range of other B-cell disorders, such as rheumatoid arthritis. Despite intensive study, the mechanism of action still remains uncertain. In the current study, anti-CD20 mAb-induced calcium signaling was investigated. Previously, we grouped anti-CD20 mAbs into Type I (rituximab-like) and Type II (B1-like) based upon various characteristics such as their ability to induce complement activation and redistribute CD20 into detergent-insoluble membrane domains. Here we show that only Type I mAbs are capable of inducing a calcium flux in B cells and that this is tightly correlated with the expression of the B-cell antigen receptor (BCR). Inhibitor analysis revealed that the signaling cascade employed by CD20 was strikingly similar to that utilized by the BCR, with inhibitors of Syk, Src, and PI3K, but not EGTA, p38, or ERK1/2, completely ablating calcium flux. Furthermore, binding of Type I but not Type II mAbs caused direct association of CD20 with the BCR as measured by FRET and resulted in the phosphorylation of BCR-specific adaptor proteins BLNK and SLP-76. Crucially, variant Ramos cells lacking BCR expression but with unchanged CD20 expression were completely unable to induce calcium flux following ligation of CD20. Collectively, these data indicate that CD20 induces cytosolic calcium flux through its ability to associate with and "hijack" the signaling potential of the BCR. 相似文献
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Addition of 2-(3-chloro-4-trifluoromethyl)anilino-3,5-dinitrothiophene (ANT2p) to detergent-solubilised Photosystem II (PS II) particles results in the photo-oxidation of carotenoid and inhibition of the steady-state oxygen-evolution rate. It has been proposed that ANT2p may modify the water-splitting reactions by mediating the transfer of reducing equivalents from endogenous electron donors, such as carotenoid, to the S2 and S3 oxidation states of PS II. In this paper we present evidence indicating that ANT2p can interact with PS II at two separate loci. The water-splitting complex is shown to be the primary site of attack by ANT2p, since artificial electron donors, such as 1,5-diphenylcarbazide (DPC), can restore PS II photochemical activity by feeding reducing equivalents directly to the reaction centre. The ANT2p interaction at this site is light-intensity dependent. A second inhibitory site close to the reaction centre P-680 chlorophyll is detected at slightly higher ANT2p concentrations. The inhibition at this site is unaffected either by changes in the actinic light intensity or by the addition of electron donors. The flash-induced oxidation of carotenoid has an ANT2p concentration dependence and an insensitivity to DPC which suggests that it results from the inhibition of the reaction centre and not with that of the water-splitting complex. 相似文献
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Rabbit platelets were labeled in vivo with 35S for characterization of platelet sulfated glycosaminoglycan. When rabbit platelets were aggregated by ADP, sulfated proteoglycan was lost from the platelet surface although no release of granule contents occurred. The sulfated proteoglycan contained in the granules of platelets pretreated with ADP was subsequently released by treatment with thrombin. The 35S-labeled proteoglycan from both sources was isolated by gel filtration and the glycosaminoglycan portion of the proteoglycan was characterized as chondroitin 4-sulfate by examining the products of digestion with hyaluronidase, chondroitinase AC and ABC, and chondro-4- and 6-sulfatases; by identification of the hexosamine as N-acetylgalactosamine; by determination of a 1 : 1 : 1 molar ratio of N-acetylgalactosamine, uronic acid and inorganic sulfate; and by cetylpyridinium chloride cellulose chromatography. In these studies, the use of 35S-labeled proteoglycan made possible detection and quantification of much smaller amounts of material than would be possible with unlabeled material. Chondroitin 4-sulfate was the only sulfated glycosaminoglycan identified in the proteoglycan lost from the platelet surface during ADP-induced aggregation and in the proteoglycan released from the granules when the platelets were exposed to thrombin. 相似文献
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Immunogenicity of a killed whole Neospora caninum tachyzoite preparation formulated with different adjuvants 总被引:3,自引:0,他引:3
Andrianarivo AG Choromanski L McDonough SP Packham AE Conrad PA 《International journal for parasitology》1999,29(10):1613-1625
A killed whole Neospora caninum tachyzoite preparation was formulated with various adjuvants and tested for its immunogenicity in cattle. The adjuvants used were: Havlogen, a polymer of acrylic acid cross-linked with polyallylsucrose; Polygen, a non-particulate copolymer; a mixture of Havlogen and Bay R-1005, which is a preparation of free base synthetic glycolipids; and Montanide ISA 773, a water-in-oil emulsion made with a mixture of metabolisable and mineral oils. Immune responses in immunised cattle were compared with those of cattle experimentally infected with culture-derived N. caninum tachyzoites. The overall mean serum IFAT titres were significantly higher (P < 0.05) in experimentally infected cattle compared with all immunised cattle. Nonetheless, the maximum antibody titres of the immunised cattle, which were obtained following the third immunisation, were within the range of titres previously described for naturally infected cattle. The overall mean serum IFAT titres were significantly higher (P < 0.05) in cattle immunised with the killed tachyzoite preparation formulated with Polygen and with the mixture of Havlogen and Bay R-1005, compared with cattle immunised with the Havlogen- and Montanide-based preparations. Two of the four adjuvant preparations were able to induce cell-mediated immune responses similar to those of the experimentally infected cattle. The Havlogen-adjuvanted tachyzoite preparation elicited N. caninum-specific proliferation of peripheral blood mononuclear cells statistically similar (P = 0.095) to that of the infected animals. Peripheral blood mononuclear cells from animals immunised with the Polygen-adjuvanted tachyzoite preparation produced interferon-gamma concentrations of similar magnitude (P = 0.17) to those from the infected animals. Polygen was one of two adjuvants that elicited the highest antibody responses, and was the only adjuvant that induced interferon-gamma levels similar to those of the infected heifers. 相似文献
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Gaydos JK Miller WA Johnson C Zornetzer H Melli A Packham A Jeffries SJ Lance MM Conrad PA 《The Journal of parasitology》2008,94(6):1264-1268
Feces of harbor seals (Phoca vitulina richardsi) and hybrid glaucous-winged/western gulls (Larus glaucescens / occidentalis) from Washington State's inland marine waters were examined for Giardia and Cryptosporidium spp. to determine if genotypes carried by these wildlife species were the same genotypes that commonly infect humans and domestic animals. Using immunomagnetic separation followed by direct fluorescent antibody detection, Giardia spp. cysts were detected in 42% of seal fecal samples (41/97). Giardia-positive samples came from 90% of the sites (9/10) and the prevalence of positive seal fecal samples differed significantly among study sites. Fecal samples collected from seal haulout sites with over 400 animals were 4.7 times more likely to have Giardia spp. cysts than samples collected at smaller haulout sites. In gulls, a single Giardia sp. cyst was detected in 4% of fecal samples (3/78). Cryptosporidium spp. oocysts were not detected in any of the seals or gulls tested. Sequence analysis of a 398 bp segment of G. duodenalis DNA at the glutamate dehydrogenase locus suggested that 11 isolates originating from seals throughout the region were a novel genotype and 3 isolates obtained from a single site in south Puget Sound were the G. duodenalis canine genotype D. Real-time TaqMan PCR amplification and subsequent sequencing of a 52 bp small subunit ribosomal DNA region from novel harbor seal genotype isolates showed sequence homology to canine genotypes C and D. Sequence analysis of the 52 bp small subunit ribosomal DNA products from the 3 canine genotype isolates from seals produced mixed sequences at could not be evaluated. 相似文献
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Photoelectric currents across planar bilayer membranes containing bacterial reaction centers. Response under conditions of single electron turnover. 总被引:2,自引:0,他引:2 下载免费PDF全文
Light-induced electric current and potential responses have been measured across planar phospholipid membranes containing reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides. Under conditions in which the reaction centers are restricted to a single electron turnover, the responses can be correlated with the light-induced electron transfer reactions associated with the reaction center. The results indicate that electron transfer from the bacteriochlorophyll dimer to the primary ubiquinone molecule, and from ferrocytochrome c to the oxidized dimer occur in series across the planar membrane. Electron transfer from the primary to secondary ubiquinone molecule is not electrogenic. 相似文献