Increased Expression of Serine Palmitoyltransferase (SPT) in Balloon-injured Rat Carotid Artery

The response to vascular injury is a complex wound healing response involving cell proliferation, migration, remodeling and inflammation. In the present studies we employed a rat balloon angioplasty model of vascular injury to investigate the potential role of sphingolipid signaling in the response to vascular injury. The enzyme serine palmitoyltransferase (SPT) catalyzes the first committed step in de novo sphingolipid biosynthesis. We observed marked upregulation of expression of both SPT subunits in actively proliferating cells in injured vessels. This enhanced SPT expression occurs in de-differentiated fibroblasts and proliferating vascular smooth muscle cells. The upregulation is particularly apparent in the proliferating luminal edge of the neointima and the adventitial de-differentiated fibroblasts and may serve as a hallmark of this process. The possible functional consequences of this enzyme upregulation and its role in the response to vascular injury are suggested but remain to be determined.

Alopecia areata incognita in Cronkhite-Canada syndrome

Cronkhite-Canada syndrome is an acquired inflammatory polyposis syndrome in which alopecia, onychomadesis and hyperpigmentation occur concurrently with gastrointestinal symptoms. The pathophysiology of alopecia in Cronkhite-Canada syndrome has not been definitively elucidated. We present evidence for alopecia areata incognita as a possible mechanism of hair loss.

A monoclonal antibody against hinge-cleaved IgG restores effector function to proteolytically-inactivated IgGs in vitro and in vivo

We report a chimeric monoclonal antibody (mAb) directed to a neo-epitope that is exposed in the IgG lower hinge following proteolytic cleavage. The mAb, designated 2095-2, displays specificity for IdeS-generated F(ab')₂ fragments, but not for full-length IgG or for closely-related F(ab')₂ fragments generated with other proteases. A critical component of the specificity is provided by the C-terminal amino acid of the epitope corresponding to gly-236 in the IgG1 (also IgG4) hinge. By its ability to bind to IdeS-cleaved anti-CD20 mAb, mAb 2095-2 fully restored antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against WIL2-S cells to the otherwise inactive anti-CD20 IgG1 F(ab')₂ fragment. Similarly, 2095-2 reinstated ADCC against MDA-MB-231 cells to an anti-CD142 IgG1 F(ab')₂ fragment. mAb 2095-2 was also capable of eliciting both CDC and ADCC to IgG4 F(ab')₂ fragments, an IgG subclass that has weaker ADCC and CDC when intact relative to intact IgG1. The in vitro cell-based efficacy of 2095-2 was extended to the in vivo setting using platelets as a cell clearance surrogate. In a canine model, the co-administration of 2095-2 together with IdeS-generated, platelet-targeting anti-CD41/61 F(ab')₂ fragment not only restored platelet clearance, but did so at a rate and extent of clearance that exceeded that of intact anti-CD41/61 IgG at comparable concentrations. To further explore this unexpected amplification effect, we conducted a rat study in which 2095-2 was administered at a series of doses in combination with a fixed dose of anti-CD41/61 F(ab')₂ fragments. Again, the combination, at ratios as low as 1:10 (w/w) 2095-2 to F(ab')₂, proved more effective than the anti-CD41/61 IgG1 alone. These findings suggest a novel mechanism for enhancing antibody-mediated cell-killing effector functions with potential applications in pathologic settings such as tumors and acute infections where protease activity is abundant.

The role of interchain disulfide bond in a recombinant human interleukin-17A variant

Interleukin-17A (IL-17A) is the prototype of IL-17 family and has been implicated in the pathogenesis of a variety of autoimmune diseases. Therefore its structural and functional properties are of great medical interest. During our research on a recombinant human IL-17A (rhIL-17A) variant, four isoforms were obtained when it was refolded. While isoforms 1 and 2 represented non-covalent dimers, isoforms 3 and 4 were determined to be covalent dimers. All four isoforms were structurally similar by Circular Dichroism and fluorescence spectroscopy studies, but differential scanning calorimetry demonstrated thermal stability in the order of isoform 1=isoform 2<isoform 4<isoform 3. In addition, compared to covalent dimers (isoform 3 and 4), the non-covalent dimers (isoforms 1 and 2) are slightly less active in a receptor-binding assay but at least 5-fold less active in a cell-based assay.

Autosomal recessive chronic granulomatous disease presenting with cutaneous dermatoses and ocular infection

Dermatoses such as eczematous dermatitis and cutaneous infection are recognized presentations of primary immunodeficiency (PID). However, atopic dermatitis affects approximately 10% of infants, and cutaneous infections are not uncommon in children, therefore the challenge for the dermatologist is to distinguish the few patients that have PID from the many that do not. We report on a 6-year-old girl who was ultimately diagnosed with autosomal recessive chronic granulomatous disease (AR-CGD) after presenting to various hospitals with dermatitis, scalp plaques recalcitrant to treatment, and recurrent infections over a 3-year period, and describe some aspects of her diagnosis and management. This report highlights the importance of considering rare disorders such as AR-CGD in the differential diagnosis of recurrent or recalcitrant dermatological infections in children.

Resistin is elevated following traumatic joint injury and causes matrix degradation and release of inflammatory cytokines from articular cartilage in vitro

OBJECTIVE

Resistin is a secreted factor that is elevated in rheumatoid arthritis (RA) and believed to drive joint inflammation in vivo. This study was undertaken to determine if resistin is present in the joint following joint injury and to elucidate the role of resistin in cartilage degradation.

METHODS

The level of resistin was measured in paired synovial fluid (SF) and serum samples from patients following joint injury (anterior cruciate ligament, ACL or meniscus tear). Localization of resistin was visualized by immunohistochemistry of synovial tissue and cartilage from healthy and OA donors. Mouse and human cartilage cultures were used to assess the effect of resistin on cartilage metabolism.

RESULTS

In trauma patients, resistin levels declined with increasing time post injury. The resistin levels were highest in samples collected up to 1 week following traumatic injury (SF: 2980 pg/ml, serum: 7901 pg/ml) and lowest in samples collected 6-26 years post injury (SF: 686 pg/ml, serum: 5682 pg/ml). Resistin was shown to be expressed in macrophage-like cells in both healthy and OA synovial tissue. Treatment of mouse cartilage cultures with recombinant resistin led to a dose dependent loss of proteoglycan and induction of inflammatory cytokine and PGE(2) production. Recombinant resistin inhibited proteoglycan synthesis in human cartilage explants.

CONCLUSION

Resistin is elevated both systemically and locally in the weeks immediately following joint injury and has a direct effect on cartilage matrix turnover and cytokine production. Resistin may play a role in the early stages of trauma-induced OA and may represent a new therapeutic target to slow joint destruction in OA.

Down modulation of human TLR3 function by a monoclonal antibody

Toll-like receptors are a family of pattern-recognition receptors that contribute to the innate immune response. Toll-like receptor 3 (TLR3) signals in response to foreign, endogenous and synthetic ligands including viral dsRNA, bacterial RNA, mitochondrial RNA, endogenous necrotic cell mRNA and the synthetic dsRNA analog, poly(I:C). We have generated a monoclonal antibody (mAb CNTO2424) that recognizes the extracellular domain (ECD) of human TLR3 in a conformation-dependent manner. CNTO2424 down-regulates poly(I:C)-induced production of IL-6, IL-8, MCP-1, RANTES, and IP-10 in human lung epithelial cells. In addition, mAb CNTO2424 was able to interfere with the known TLR3-dependent signaling pathways, namely NF-kappaB, IRF-3/ISRE, and p38 MAPK. The generation of this neutralizing anti-TLR3 mAb provides a unique tool to better understand TLR3 signaling and potential cross-talk between TLR3 and other molecules.

Modulation of antigen-specific T cell response by a non-mitogenic anti-CD3 antibody

Suppression of T cell response is the key to enhance graft survival and control autoimmune diseases. A mitogenic anti-CD3 monoclonal antibody (mAb), OKT3, has been used for decades to control acute rejection in organ transplantation. Although effective, the clinical use was limited by its side effects, such as cytokine release mediated by T cell activation. A low mitogenic humanized OKT3 with reduced FcR-binding (hgammaOKT3 Ala-Ala) was generated and tested in several clinical studies. Although hgammaOKT3 Ala-Ala demonstrated maintained efficacy and better safety it still activated T cells. To investigate if a non-mitogenic anti-CD3 mAb can be equally effective in immune suppression, a chimeric non-FcR-binding anti-mouse CD3 mAb (anti-CD3 IgG2a Ala-Ala) was generated. Unlike the hgammaOKT3 Ala-Ala, the mouse IgG2a Ala-Ala anti-CD3 mAb did not induce T cell activation as measured by proliferation, cytokine production and apoptosis. Nevertheless, the IgG2a Ala-Ala anti-CD3 mAb was equally effective in the inhibition of antigen-specific CD4+ T cell activation in vitro to that of the mitogenic anti-CD3 mAb (Anti-CD3 IgG2a). In vivo, the IgG2a Ala-Ala anti-CD3 mAb only induced transient reduction of peripheral and spleen T cells and did not trigger detectable cytokine release. Nonetheless, this non-mitogenic anti-CD3 mAb significantly prolonged islet graft survival as effectively as the mitogenic anti-CD3 mAb in an allogenic islet transplantation model. These results demonstrated that a non-mitogenic anti-CD3 mAb could be used as an effective immune modulator. It may also indicate that a true non-mitogenic version of OKT3 could further improve its safety profile for clinical use.

A novel site contributing to growth-arrest-specific gene 6 binding to its receptors as revealed by a human monoclonal antibody

Gas6 (growth-arrest-specific gene 6) is a vitamin K-dependent protein known to activate the Axl family of receptor tyrosine kinases. It is an important regulator of thrombosis and many other biological functions. The C-terminus of Gas6 binds to receptors and consists of two laminin-like globular domains LG1 and LG2. It has been reported that a Ca2+-binding site at the junction of LG1 and LG2 domains and a hydrophobic patch at the LG2 domain are important for receptor binding [Sasaki, Knyazev, Cheburkin, Gohring, Tisi, Ullrich, Timpl and Hohenester (2002) J. Biol. Chem. 277, 44164-44170]. In the present study, we developed a neutralizing human monoclonal antibody, named CNTO300, for Gas6. The antibody was generated by immunization of human IgG-expressing transgenic mice with recombinant human Gas6 protein and the anti-Gas6 IgG sequences were rescued from an unstable hybridoma clone. Binding of Gas6 to its receptors was partially inhibited by the CNTO300 antibody in a dose-dependent manner. To characterize further the interaction between Gas6 and this antibody, the binding kinetics of CNTO300 for recombinant Gas6 were compared with independently expressed LG1 and LG2. The CNTO300 antibody showed comparable binding affinity, yet different dependence on Ca2+, to Gas6 and LG1. No binding to LG2 was detected. In the presence of EDTA, binding of the antibody to Gas6 was disrupted, but no significant effect of EDTA on LG1 binding was evident. Further epitope mapping identified a Gas6 peptide sequence recognized by the CNTO300 antibody. This peptide sequence was found to be located at the LG1 domain distant from the Ca2+-binding site and the hydrophobic patch. Co-interaction of Gas6 with its receptor and CNTO300 antibody was detected by BIAcore analysis, suggesting a second receptor-binding site on the LG1 domain. This hypothesis was further supported by direct binding of Gas6 receptors to an independently expressed LG1 domain. Our results revealed, for the first time, a second binding site for Gas6-receptor interaction.

Downstream changes in the transport and storage of sediment-associated contaminants (P, Cr and PCBs) in agricultural and industrialized drainage basins

Samples of suspended, floodplain and channel bed sediment have been used to examine downstream changes in ediment-associated contaminant transport and storage in contrasting rivers in Yorkshire, UK. The concentrations of hosphorus, chromium and selected PCBs associated with sediment in the River Aire and its main tributary, the River Calder, which drain an urbanized and industrialized catchment, are considerably higher than those in the relatively unpolluted River Swale, which drains an agricultural catchment. Concentrations of sediment-associated contaminants in the Aire/Calder system increase downstream, reflecting the location of urban and industrial areas in the middle and lower reaches, and the location of point source inputs, such as sewage treatment works. The ontaminant concentrations associated with floodplain and channel bed sediment in the Rivers Aire and Calder are high, particularly in the lower reaches. This, combined with measurements of sediment storage on the floodplain and channel bed, indicate that significant storage of sediment-associated contaminants occurs in the Rivers Aire and Calder.

Menstrual cycle dependent fluctuations in NK and T-lymphocyte subsets from non-pregnant human endometrium

PROBLEM

To establish the relative proportions of endometrial lymphocyte subpopulations during the menstrual cycle.

METHOD OF STUDY

Lymphocytes were investigated by flow cytometry, during the early proliferative (EP), late proliferative (LP), early secretory (ES) and late secretory (LS) phases of the menstrual cycle.

RESULTS

Between the LP and LS phases, there was an increase in NK cells from 26.4% to 83.2% (P = 0.0017) of the CD45+ population. T cells decreased from 55.06% to 6.7% (P = 0.0017). Within the T-cell population, CD8+ cells decreased significantly from 63.0% in the LP phase to 54.2% in the LS phase (P = 0.04). In contrast, potential regulatory populations such as double negative (DN) T cells CD3+CD4-CD8- and natural T cells (NT) CD3+CD56+, increased significantly in the LS phase (P = 0.05; P = 0.03). gammadelta T cells, predominantly of the DN and NT phenotypes remained consistently low at all stages of the cycle (2.34%).

CONCLUSION

Endometrial lymphocyte fluctuations during the menstrual cycle may reflect hormonal regulation of maternal immunity, thereby promoting tolerance at the time of implantation.

Serine palmitoyltransferase regulates de novo ceramide generation during etoposide-induced apoptosis

The de novo pathway of sphingolipid synthesis has been identified recently as a novel means of generating ceramide during apoptosis. Furthermore, it has been suggested that the activation of dihydroceramide synthase is responsible for increased ceramide production through this pathway. In this study, accumulation of ceramide mass in Molt-4 human leukemia cells by the chemotherapy agent etoposide was found to occur primarily due to activation of the de novo pathway. However, when the cells were labeled with a substrate for dihydroceramide synthase in the presence of etoposide, there was no corresponding increase in labeled ceramide. Further investigation using a labeled substrate for serine palmitoyltransferase, the rate-limiting enzyme in the pathway, resulted in an accumulation of label in ceramide upon etoposide treatment. This result suggests that the activation of serine palmitoyltransferase is the event responsible for increased ceramide generation during de novo synthesis initiated by etoposide. Importantly, the ceramide generated from de novo synthesis appears to have a distinct function from that induced by sphingomyelinase action in that it is not involved in caspase-induced poly (ADP-ribose)polymerase proteolysis but does play a role in disrupting membrane integrity in this model system. These results implicate serine palmitoyltransferase as the enzyme controlling de novo ceramide synthesis during apoptosis and begin to define a unique function of ceramide generated from this pathway.

Optimisation of a technique for isolating lymphocyte subsets from human endometrium

Human endometrium is a rich source of lymphocytes which may have unique immunoregulatory functions. The aim of this study was to compare current procedures for endometrial tissue disaggregation, and optimise a method for isolation of endometrial lymphocytes. Tissue was obtained from 41 women undergoing elective hysterectomy or dilation and curettage (D&C) for reasons of benign non-endometrial pathology. Specimens were exposed to reduction/chelation, mechanical or enzymatic disruption. Optimal single cell suspensions of high yields (mean 8.8 x 10(6) range 3.5-18 x 10(6)lymphs) and good viability (60%) were obtained, using a combination of collagenase IV (200 U/ml) and DNase I (35 U/ml). Suspensions were further purified by density gradient centrifugation. Multi-colour flow cytometry was used for analysis of endometrial lymphocyte subsets. Cell suspensions were stained with mAbs specific for CD3, CD4, CD8, CD56, CD45 and CD14, and it was clearly shown that the developed method had no effect on surface glycoprotein expression. Phenotypic analysis revealed consistent populations of endometrial large granular lymphocytes (CD56+CD3-) 54.16%, and T-cells (CD3+) 37.73%. This technique was applicable to the characterisation of T-cell populations, including CD8+ (56.6%), CD4+ (44.0%), and particularly smaller populations of CD4+CD8+(3.56%), CD4-CD8-(3.34%) and CD56+(6.3%) due to it's sensitivity. In conclusion, optimised enzymatic digestion, in combination with flow cytometry provides an effective method for phenotypic examination of small endometrial lymphocyte subpopulations.

CD4+ CD8+ and CD8alpha+ beta- T lymphocytes in human small intestinal lamina propria

OBJECTIVE

To examine CD8 expression by T-lymphocyte subpopulations from disease-free human lamina propria.

METHODS

Single-cell suspensions were prepared from the epithelial layer and the lamina propria of small intestinal biopsies obtained endoscopically from disease-free patients. Monoclonal antibodies against CD3, CD4, CD8, CD56, CD8alphabeta, CD8alpha, TCR alphabeta and TCR gammadelta were used for dual and three-colour flow cytometric analysis.

RESULTS

In addition to classical CD4+ and CD8+ T lymphocytes a substantial proportion of lamina propria T lymphocytes were CD4+ CD8+ or 'double positive' (mean 14%, range 4-26%). This population was significantly lower in the epithelial layer of the same patients (mean 7%, range 3-21%, P < 0.007). Three-colour flow cytometric analysis revealed that expression of the CD8 molecule on double positive T cells in the lamina propria was limited to the CD8alpha chain. Furthermore, of the CD8+ population, CD8+ T cells which only expressed the alpha chain were present in greater numbers in the lamina propria (mean 35%, range 14-54%) than in the epithelial layer (mean 18%, range 5-37%, P < 0.02). NK (CD56+) cells were not detected and few gammadeltaTCR+ T lymphocytes were detected in the lamina propria (mean 2%, range 0.5-6.6%) when compared with the epithelial layer (mean 8%, range 0.2-14%, P < 0.008).

CONCLUSION

A significant population of CD4+ CD8alpha+ T lymphocytes which are CD8beta chain negative have been detected in the intestinal lamina propria. These cells form a more significant component of the lamina propria than the epithelial layer T-cell repertoire and may have a unique function in intestinal immunoregulation.

[Non-cardiogenic pulmonary edema after transfusion of plasma containing an anti-HLA-B21 antibody]

A patient with a von Willebrand factor deficiency received three units of fresh frozen plasma during a postoperative period. During the last unit transfusion she developed a severe respiratory distress and non cardiac pulmonary edema was diagnosed based upon the clinical, radiological and hemodynamic findings. Reintubation and mechanical ventilation with end-expiratory pressure were instituted leading to a complete and rapid recovery within 48 h. The serum from the last plasma donor contains an anti-HLA-B21 lymphocytotoxic antibody that did agglutinate neutrophils from HLA-B21 positive individuals. The patient's HLA type was B21. The concerned donor was a IVpar Igeste female. Two problems are evoked by this observation with regard to transfusion: first, fresh-frozen plasma was used as an inappropriate treatment for a coagulating factor deficiency, second, exclusion of this donor from a classical blood donation is needed.

Nucleotide sequence of the large double-stranded RNA segment of bacteriophage phi 6: genes specifying the viral replicase and transcriptase

The genome of the lipid-containing bacteriophage phi 6 contains three segments of double-stranded RNA. We determined the nucleotide sequence of cDNA derived from the largest RNA segment (L). This segment specifies the procapsid proteins necessary for transcription and replication of the phi 6 genome. The coding sequences of the four proteins on this segment were identified on the basis of size and the correlation of predicted N-terminal amino acid sequences with those found through analysis of isolated proteins. This report completes the sequence analysis of phi 6. This constitutes the first complete sequence of a double-stranded RNA genome virus.

Nucleotide sequence of the middle dsRNA segment of bacteriophage phi 6: placement of the genes of membrane-associated proteins

The genome of the lipid-containing bacteriophage phi 6 contains three segments of double-stranded RNA. We have determined the nucleotide sequence of cDNA derived from the middle-size RNA segment. The coding sequences of three proteins on this segment were identified on the basis of size and the correlation of predicted N-terminal amino acid sequences with those found through the analysis of isolated proteins. In contrast to our results with the small phi 6 dsRNA segment, the open reading frames are not tightly clustered. The homologous terminal noncoding regions between the middle and small dsRNA segments are found to be more extensive than RNA sequencing had previously indicated.