Immunoglobulin M-enriched human intravenous immunoglobulin prevents complement activation in vitro and in vivo in a rat model of acute inflammation

An important antiinflammatory mechanism of intravenous immunoglobulin preparations (IVIG) is their ability to block complement activation. The purpose of this study was to compare the complement-inhibitory activity of four IVIG preparations differing in isotype composition. The preparations were: (1) IVIgG (48 g/L IgG, 2 g/L IgA; Intraglobin F); (2) Pentaglobin (38 g/L IgG, 6 g/L IgM, 6 g/L IgA); (3) IVIgM (35 g/L IgM, 12 g/L IgA, 3 g/L IgG); and (4) IVIgA (41 g/L IgA, 9 g/L IgG), all from Biotest Pharma GmbH, Dreieich, Germany. Their complement inhibitory activity was assessed in vitro by measurement of the blocking of C1q-, C4-, and C3 deposition on solid-phase aggregated rabbit IgG by enzyme-linked immunosorbent assay (ELISA). Complement inhibition in this ELISA was best for IVIgM, followed by Pentaglobin and IVIgG; IVIgA did not exhibit an inhibitory effect. Control experiments with excess concentrations of C1q as well as with C1q-depleted serum showed that the inhibitory effects of IVIG were not caused by complement activation and thus, consumption, but that C4 and C3 were scavenged by IgM and to a lesser extent by IgG. These results were confirmed in vivo in the rat anti-Thy 1 nephritis model, in which a single dose of 500 mg/kg of IVIgM prevented C3-, C6-, and C5b-9 deposition in the rat glomeruli, whereas the effect of IVIgG was much less pronounced. Reduction of complement deposition was paralleled by a diminished albuminuria, which was completely absent in the IVIgM-treated rats. IVIgM and to a lesser extent IVIgG also prevented rat C3 deposition on cultured rat glomerular mesangial cells in vitro, but did not influence anti-Thy 1 binding. Neither IVIgM nor Pentaglobin nor IVIgG negatively affected in vitro phagocytosis of Escherichia coli (E coli) by human granulocytes. In conclusion, we have shown that IgM enrichment of IVIG preparations enhances their effect to prevent the inflammatory effects of complement activation.

Control of monocyte influx in glomerulonephritis in transplanted kidneys in the rat

Induction of anti-Thy-1 nephritis in different strains of inbred rats results in phenotypically different types of renal diseases. In Wistar and Lewis (LEW) rats, a transient influx of ED1+ macrophages occurs 24 hours after injection of anti-Thy-1 antibodies, whereas this does not occur in F344 rats. The present experiments were designed to investigate the role of the kidney in the regulation of the monocyte influx in this model. To dissociate the role of the immune system from local intrarenal factors in the control of monocyte influx, anti-Thy-1 nephritis was induced in LEW rats with an F344 kidney transplant and in F344 rats with a LEW kidney allograft. Acute rejection episodes were prevented by treatment with an anti-CD4 monoclonal antibody. Control rats received a syngeneic kidney graft. Monocyte influx after injection of anti-Thy-1 antibodies was found in the glomeruli of both LEW and F344 kidneys removed from LEW recipients, whereas there was no demonstrable monocyte influx after infusion of anti-Thy-1 antibodies in either LEW or F344 kidneys removed from F344 recipients. Monocyte infiltration correlated with the subsequent expansion of the mesangial extracellular matrix. The inability to attract monocytes was not due to the lack of glomerular expression of chemokines, because F344 and LEW glomeruli demonstrated a similar expression of monocyte chemoattractant protein-1 (MCP-1). Differences in the ability to activate the complement system were excluded. We conclude that the immune system controls the glomerular influx of monocytes and that the reaction of the mesangial cells is probably controlled by combinations of cytokines produced during the inflammatory process.

Visceral glomerular epithelial cell DNA synthesis in experimental and human membranous disease

BACKGROUND

Membranous nephropathy (MN) is a 'non-proliferative' glomerulonephritis. However, visceral glomerular epithelial cell (vGEC) proliferating cell nuclear antigen staining and increased glomerular histone mRNA in passive Heymann nephritis (PHN), suggest that vGECs may enter the cell cycle and undergo DNA synthesis. We used in situ hybridisation for histone mRNA, an S-phase specific marker, to investigate this possibility and identify the cellular origin of histone mRNA in PHN and MN.

METHODS

PHN was induced in 16 Sprague-Dawley rats. There were 8 saline/serum controls. 12 animals were sacrificed on days 5 and 10. Renal biopsies from 10 proteinuric cases with MN and matched controls were studied.

RESULTS

Day-5 Heymann animals demonstrated more S-phase cells/glomerulus than controls (0.53 +/- 0.09 vs. 0.195 +/- 0.045; p < 0.01). Glomerular S-phase cells were also increased in patients compared to controls (0.24 +/- 0.07 vs. 0.04 +/- 0.018; p < 0.03). In both experimental and human MN, the peripheral location and morphology of glomerular histone mRNA-positive cells was typical of vGECs.

CONCLUSION

The results in PHN indicate that vGECs recently injured with antibody and complement enter into the cell cycle and undergo DNA synthesis. The S-phase vGECs in MN may indicate the persistence of immune injury. Whether or not this process leads to cell replication is open to question.

The monoclonal antibody AS02 recognizes a protein on human fibroblasts being highly homologous to Thy-1

Recently, we described a novel fibroblast-restricted monoclonal antibody (mAb AS02) that recognizes a membrane-bound antigen. Characterization and isolation of the corresponding antigen showed that mAb AS02 recognized a protein on human fibroblasts that is highly homologous or identical to human Thy-1 antigen (CD90). Partial amino acid sequencing of the corresponding mAb AS02 antigen and comparison with known proteins revealed a 100% homology of the sequenced peptides to the human Thy-1 antigen. Cross-immunodepletion studies with mAb AS02 and an anti-Thy-1 antibody confirmed these results. Utilizing two-dimensional (2D) gel electrophoresis of fibroblast cell extracts and purified antigen, mAb AS02 and the anti-Thy-1-antibody recognized identical protein spots. Furthermore, we demonstrated many identical biochemical properties of the corresponding AS02 antigen and Thy-1 antigen, such as the molecular weight of the core protein and deglycosylation products and the detection of a GPI anchor. In functional assays, the attachment of fibroblasts to collagen I and fibronectin was increased after incubation of fibroblasts with mAb AS02. Therefore, the Thy-1 antigen appears to be involved in the regulation of the adherence of human dermal fibroblasts.

Anti-vitronectin antibodies enhance anti-Thy-1-induced proteinuria in PVG/c, but not in Wistar rats

Injection of rats with mouse monoclonal IgG2a anti-Thy1.1 antibodies (ER4G) results in rapid development of proteinuria in Wistar rats, reaching average values of 160 mg/24 h on day 3 after antibody administration. In contrast, no overt proteinuria was observed in PVG/c+ rats (maximum, 40 mg/24 h on day 3). This study investigates whether differences in the inactivation of C5b-9 complexes in the glomerulus by complement inhibitors are responsible for the differences in proteinuria between the two rat strains. Regardless of the presence of proteinuria, an increased expression of Crry by mesangial cells (MC) was observed within 24 h after injection of ER4G in both Wistar and PVG/c+ rats. Double-label immunofluorescence using goat anti-mouse Ig antibodies demonstrated an expression of Crry exclusively on MC. Furthermore, Crry colocalized with C5b-9 complexes on MC, as detected by a monoclonal antibody against the rat C5b-9 neo-antigen. In PVG/c+ rats, C5b-9 complexes persisted in the mesangial area for at least 7 d and colocalized immediately (within 1 h) and homogeneously with vitronectin. However, in proteinuric Wistar rats, C5b-9 complexes disappeared from the glomerular mesangium within 6 d. In these rats, mesangial colocalization of C5b-9 with vitronectin could only occasionally be detected. Pretreatment of PVG/c+ rats with antibodies against vitronectin, followed by administration of ER4G, resulted in the immediate development of proteinuria (maximum, 119 mg/24 h on day 3; P < 0.05), whereas Wistar rats did not become more proteinuric. This study provides evidence that differences in susceptibility of PVG/c+ and Wistar rats to complement-mediated damage of the glomerulus may be related to the degree of inactivation of C5b-9 complexes by complement regulatory factors.

Functional heterogeneity of Thy-1 membrane microdomains in rat basophilic leukemia cells

Antibody-mediated cross-linking of Thy-1 glycoprotein on the surface of rat mast cells and rat basophilic leukemia (RBL) cells initiates biochemical events which culminate in secretion of allergy mediators. Thy-1, like some other glycosylphosphatidylinositol (GPI)-anchored proteins, forms detergent-insoluble complexes containing protein tyrosine kinases (PTK) and some other molecules which are implicated in the signaling pathway. On the surface of a rat mast cell there are more than 10(6) Thy-1 molecules; however, it is not known which fraction of them is involved in transmembrane signaling, and what exactly is the heterogeneity of Thy-1 complexes. Using sucrose density gradient ultracentrifugation of detergent-lysed RBL cells we found that the density of Thy-1 complexes depended on the detergent used and the lysis conditions employed. Sepharose 4B gel chromatography fractionation followed by density gradient ultracentrifugation revealed both size and density heterogeneity of Thy-1 and Lyn PTK complexes. Cross-linking of surface Thy-1 caused significant changes in the density of these complexes, and an increase in Lyn kinase activity in low/medium-density fractions. Thy-1 in low-density fractions was relatively resistant to cleavage with phosphatidylinositol-specific phospholipase C (PI-PLC). Interestingly, removal of only a small fraction of surface Thy-1 by PI-PLC abolished the cell activation as determined by tyrosine phosphorylation of certain proteins. When Triton X-100 lysates were fractionated at 12000 x g, about 50 % of Thy-1 remained associated with the nuclear/cytoskeleton pellet; this fraction of Thy-1 exhibited an increased sensitivity to PI-PLC. Confocal laser scanning microscopy on fixed cells revealed that the total Thy-1 was relatively homogeneously distributed over the plasma membrane, whereas the PI-PLC-resistant Thy-1 was found mostly in small clusters. The combined data suggest that specialized membrane microdomains enriched in Thy-1 with increased sensitivity to PI-PLC are directly involved in coupling Thy-1 aggregation to transmembrane signaling.

Antigen-presenting cell function of epidermal cells activated by hapten application

Exposure to haptens initiates a series of immune and inflammatory reactions that cause migration of epidermal Langerhans cells (LC) to draining lymph nodes, antigen processing, and presentation to T cells. In the present study, the antigen-presenting cell (APC) function of epidermal cells (EC) following hapten application was determined using a cell transfer system. This function of EC in inducing contact sensitivity (CS) in the recipient mice appeared as early as 6 h after hapten painting, and reached its maximum at 24 h. The amount of hapten on EC did not correlate with the function, i.e. the amount retained on the cells was greatest immediately after hapten painting and decreased over time. Several experiments were performed to identify the cell type responsible for the APC function. Through immunomagnetic bead separation, the APC function was detected in Ia- EC, as well as in unfractionated EC from hapten-painted mice. A purified population of Ia+ cells (LC) induced CS with much less efficiency than unseparated cells. Depletion of LC by anti-Ia monoclonal antibody (mAb) and complement-mediated lysis did not impair the APC function, whereas it was reduced by the depletion of Thy-1+ cells by anti-Thy-1 mAb and complement-mediated lysis. Moreover, adherent cells that were harvested from a 48-h culture of EC obtained from hapten-painted skin, and were free of contaminating LC and gamma omega T cells, had a strong capacity to induce CS. These findings indicate that keratinocytes (KC) acquire APC function as well as LC, with hapten application. Phenotypically increased expression of intercellular adhesion molecule-1 (ICAM-1) and Thy-1 on EC was observed following hapten application, whereas expression of Ia and B7/BB1 was unaltered. The APC function of EC from hapten-painted skin was dependent on ICAM-1 and Thy-1 expression, as the mAbs for these molecules reduced the capacity to induce CS. These results suggest that hapten application induces not only LC but also KC to mature functionally and become potent APCs, and that these KC exert the APC function complementarily at local sites following the migration of LC with potent APC function to the draining lymph node.

Mucosal immunity to herpes simplex virus type 2 infection in the mouse vagina is impaired by in vivo depletion of T lymphocytes

Intravaginal (IVAG) inoculation of wild-type herpes simplex virus type 2 (HSV-2) in mice causes epithelial infection followed by lethal neurological illness, while IVAG inoculation of attenuated HSV-2 causes epithelial infection followed by development of protective immunity against subsequent IVAG challenge with wild-type virus. The role of T cells in this immunity was studied by in vivo depletion of these cells with monoclonal antibodies. Three groups of mice were used for each experiment: nonimmune/challenged mice, immune/challenged mice, and immune depleted mice [immune mice depleted of a T-cell subset(s) shortly before challenge with HSV-2]. Mice were assessed for epithelial infection 24 h after challenge, virus protein in the vaginal lumen 3 days after challenge, and neurological illness 8 to 14 days after challenge. Monoclonal antibodies to CD4, CD8, or Thy-1 markedly reduced T cells in blood, spleen, and vagina, but major histocompatibility complex class II antigens were still partially upregulated in the vaginal epithelium after virus challenge, indicating that virus-specific memory T-cell function was not entirely eliminated from the vagina. Nevertheless, immune mice depleted of CD4+ and CD8+ T cells, Thy-1+ T cells, or CD8+ T cells alone had greater viral infection in the vaginal epithelium than nondepleted immune mice, indicating that T cells contribute to immunity against vaginal HSV-2 infection. All immune depleted mice retained substantial immunity to epithelial infection and were immune to neurological illness, suggesting that other immune mechanisms such as virus-specific antibody may also contribute to immunity.

Induced expression of Thy-1 molecules on dermal endothelial cells in skin allografts

We obtained evidence in a foregoing study that inducible Thy-1 on vascular endothelial cells functions as a possible vascular permeability modulator in the rat. We now report on the regulation and function of endothelial Thy-1 in skin allograft rejection in the rat. While no obvious expression of Thy-1 antigen on the vasculature can be seen in normal organs, dermal endothelial cells do express Thy-1 during allogeneic skin graft rejection and Freund's complete adjuvant (FCA)-induced inflammation. The antigen was weakly induced on tubular epithelial, but not on endothelial cells during kidney allograft rejection, and not in FCA-induced inflammation of the kidney. In contrast, Thy-1 antigen was not induced in the rejected lung or in FCA-induced inflammation of the lung. This pattern of Thy-1 regulation was transcriptionally regulated. Administration of anti-Thy-1 antibodies generated increased vascular permeability in skin allografts, although this procedure did not modulate survival of the grafts.

Suppression of rat bone marrow cells by Friend murine leukemia virus envelope proteins

In a retroviral rat model, we have investigated the nontransforming effects of murine leukemia virus FB29 on the bone marrow. Upon intraperitoneal inoculation with murine leukemia virus FB29 of either neonatal or adult rats, bone marrow cells became massively infected within the first 12 days postinoculation. In neonatally inoculated rats, a persistent productive bone marrow infection was established, whereas in rats inoculated as adults, no infected bone marrow cells could be detected beyond 12 days postinoculation. Retroviral infection was most likely cleared by an antiviral immune response (Hein et al., 1995, Virology 211, 408-417). Exposure to virus irreversibly decreased numbers of bone marrow cells staining with monoclonal antibody OX7 by 10-30%. Reduction of OX7+ bone marrow cells by 20% was also observed in vitro, after bone marrow cells from uninfected adult rats had been co-incubated with virus. FB29-envelope proteins were sufficient alone to reduce numbers of OX7+ bone marrow cells, both in vivo and in vitro. According to results on incorporation of propidium iodide, decreased numbers of OX7+ cells were due to cell death. By flow cytometric analyses OX7+ bone marrow cells as well as monocytes/macrophages were identified to be major target cells for infection with FB29 within the bone marrow. Thus, the mechanism(s) responsible for death of OX7+ bone marrow cells might be due to direct toxicity of viral envelope proteins and/or to interactions of viral envelope proteins with cells of the monocytic lineage.

High doses of purified stem cells cause early hematopoietic recovery in syngeneic and allogeneic hosts

In humans, autologous transplants derived from bone marrow (BM) usually engraft more slowly than transplants derived from mobilized peripheral blood. Allogeneic BM transplants show a further delay in engraftment and have an apparent requirement for donor T cells to facilitate engraftment. In mice, Thy-1.1(lo)Lin-/loSca-1+ hematopoietic stem cells (HSCs) are the principal population in BM which is responsible for engraftment in syngeneic hosts at radioprotective doses, and higher doses of HSCs can radioprotect an allogeneic host in the absence of donor T cells. Using the mouse as a preclinical model, we wished to test to what extent engraftment kinetics was a function of HSC content, and whether at high doses of c-Kit+Thy-1.1(lo)Lin-/loSca-1+ (KTLS) cells rapid allogeneic engraftment could also be achieved. Here we demonstrate that engraftment kinetics varied greatly over the range of KTLS doses tested (100-10,000 cells), with the most rapid engraftment being obtained with a dose of 5,000 or more syngeneic cells. Mobilized splenic KTLS cells and the rhodamine 123(lo) subset of KTLS cells were also able to engraft rapidly. Higher doses of allogeneic cells were needed to produce equivalent engraftment kinetics. This suggests that in mice even fully allogeneic barriers can be traversed with high doses of HSCs, and that in humans it may be possible to obtain rapid engraftment in an allogeneic context with clinically achievable doses of purified HSCs.

Source of reactive oxygen species in anti-Thy1 nephritis

In proliferative glomerulonephritis, both macrophages and mesangial cells generate reactive oxygen species (ROS), contributing to the development of glomerular injury. We have attempted to determine which cell produces ROS during anti-Thy1 nephritis (ATN) in rats. The generation of ROS was studied using luminol amplified chemiluminescence (GCL) on isolated glomeruli. Immunohistochemical studies used avidin-biotin complex (ABC) to label macrophages and mesangial cells. Immediately after ATN induction, mesangiolysis and infiltration with ED-1 positive cells (referred to as macrophage) was noted with a peak at day 1. After day 4, mesangial proliferation appeared with a decrease of the ED-1 positive cells and a prominent increase of PCNA positive cells (regarded as mesangial cells). In the early phase of ATN, GCL, reflecting ROS generation, increased along with the appearance of ED-1 positive cells. GCL subsequently decreased as mesangial cells increased. This suggested that macrophage were the principal participants in ROS generation in the early phase of ATN although mesangial cells cannot be completely disregarded in the generation of ROS and development of glomerular injury.

Dendritic cells and resting B cells form clusters in vitro and in vivo: T cell independence, partial LFA-1 dependence, and regulation by cross-linking surface molecules

Initiation of an Ab response requires interaction between dendritic cells (DC), T cells, and B cells in a T cell area. We demonstrate that rat DC and B cells form T cell-independent clusters in vitro and in vivo. In vitro clusters form within 1 h and dissociate within 24 to 48 h. Clustering is restricted to resting B cells, is energy, cytoskeleton, and protein kinase C dependent, and is inhibited by anti-LFA-1 but not anti-ICAM-1 mAbs. Spleen and lymph node B cells cluster more strongly than those from lymph or blood, suggesting up-regulation of adhesiveness during transendothelial migration. Bone marrow B cells do not form clusters. DC from spleen and lymph nodes show the most clustering, lymph-borne DC are intermediate, and DC from lamina propria, Peyer's patches, and those grown from bone marrow form the fewest clusters. Clustering is stimulated by cross-linking MHC class II (whole mAb or F(ab')2) on DC or B cells or Thy-1 on DC, but not MHC class I, CD45, or CD44. Stimulation by mAb is energy, cytoskeletal, and protein kinase C dependent, but is not inhibited by anti-LFA-1 mAbs, suggesting involvement of other, unidentified adhesion molecules. We suggest that interactions between DC and B cells will occur regularly during B cell recirculation. Cross-linking of MHC class II-peptide molecules on DC by specific T cells would increase binding avidity, causing retention of Ag-specific B cells on DC long enough for the B cells to process Ag, thereby facilitating cognate interactions between T and B cells.

Thy-1 is a component common to multiple populations of synaptic vesicles

Thy-1, a glycosylphosphatidylinositol-linked integral membrane protein of the immunoglobulin superfamily, is a component of both large dense-core and small clear vesicles in PC12 cells. A majority of this protein, formerly recognized only on the plasma membrane of neurons, is localized to regulated secretory vesicles. Thy-1 is also present in synaptic vesicles in rat central nervous system. Experiments on permeabilized PC12 cells demonstrate that antibodies against Thy-1 inhibit the regulated release of neurotransmitter; this inhibition appears to be independent of any effect on the Ca2+ channel. These findings suggest Thy-1 is an integral component of many types of regulated secretory vesicles, and plays an important role in the regulated vesicular release of neurotransmitter at the synapse.

Fas ligand- mediated killing by intestinal intraepithelial lymphocytes. Participation in intestinal graft-versus-host disease

In vitro studies have demonstrated that intestinal intraepithelial lymphocytes (IEL) are constitutively cytotoxic; however, the mechanism and target of their cytotoxicity are unknown. Apoptosis of intestinal epithelial cells (IEC) and an increase in IEL numbers are classical signs of intestinal graft-versus-host disease (GVHD), although whether IEL can mediate IEC apoptosis directly in GVHD is unclear. Recent evidence suggests that target epithelial organ injury observed in GVHD is predominantly Fas-mediated; therefore, we investigated the possibility that IEL induce apoptosis of IEC through a Fas-mediated mechanism. Here, we demonstrate that the IEL isolated from normal mice readily display potent Fas ligand (FasL)-mediated killing activity after CD3 stimulation, and that IEC express Fas, suggesting that IEC are potential targets for FasL-mediated killing by IEL. In vitro, IEL isolated from GVHD mice have markedly increased FasL-mediated killing potential and are spontaneously cytolytic toward host-derived tumor cells predominantly through a Fas-mediated pathway. In vivo transfer of IEL isolated from GVHD mice induced significantly more IEC apoptosis in F1 wild-type mice than in Fas-defective F1lpr mice. Thus, these results demonstrate that FasL-mediated death of IEC by IEL is a major mechanism of IEC apoptosis seen in GVHD.

Genes of the immune system cosegregate with the age at onset of diabetes in the BB/OK rat

The knowledge of genetic factors determining the age at onset of diabetes may help to delay the development of diabetes and its complications. This prompted us to use our well-characterized BB/OK rat whose age at onset of diabetes can change from 50 to more than 400 days for crossing studies to search for loci cosegregating with the age at onset. Fifty-nine diabetic first backcross hybrids resulting from crosses between diabetic BB/OK and diabetes-resistant DA and SHR rats were genotyped with PCR-analyzed microsatellite markers located on 21 chromosomes. Loci on chromosomes 6 (Ighe -D6Mgh2) and 8 (D8Mit2- Apoc3) were linked with the age at onset. Hybrids which were homozygous for the BB alleles developed significantly earlier diabetes than hybrids which were heterozygous The difference between the age at onset of heterozygous and homozygous hybrids reached a maximum at the loci Ighe on chromosome 6 (+ 32 days, p = 0.0018) and D8Mit2 on chromosome 8 (+ 28 days, p = 0.007). Candidate genes around the loci linked with the age at onset of diabetes are involved in the humoral and cellular immune response. For the first time, this study provides evidence that genetic factors can affect the age at onset of diabetes in the rat.

Thymic function can be accurately monitored by the level of recent T cell emigrants in the circulation

Expression of the avian chT1 thymocyte antigen persists on a subpopulation of peripheral T cells enriched in the DNA deletion circles created by alphabeta and gammadelta TCR gene rearrangements. The chT1+ cells are evenly distributed among all of the peripheral T lymphocyte compartments. The levels of chT1+ T cells in the periphery gradually decline in parallel with age-related thymic involution, and these cells disappear following early thymectomy. Experiments in which variable numbers of the 14 thymic lobes are removed in young chicks indicate a direct correlation between the levels of circulating chT1+ cells and residual thymic mass. Measurement of recent thymic emigrants in the periphery thus provides an accurate indication of thymic function.

A molecular basis for species differences in Thy-1 expression patterns

Thy-1 is a membrane glycoprotein that displays species-specific differences in its pattern of expression. Although it is expressed on thymocytes and splenocytes in mice, it is only expressed on thymocytes in rats. Based on previous studies suggesting that the third intron of the mouse Thy-1 gene is required for its expression in thymocytes, in vivo footprinting analysis was performed on the third introns of both the mouse and rat Thy-1 genes, and led to the identification of homologous 36 bp "footprinted" regions. The mouse 36 bp region was found to be capable of specifically binding an Ets-1-like nuclear factor present in both mouse thymocytes and splenocytes. In contrast, the homologous 36 bp region of the rat which differs from the mouse 36 bp region by three nucleotides resulting in the loss of the Ets-1 binding site, is unable to bind a similar Ets-1-like factor present in rat thymocytes. Instead, this region of the rat third intron binds another nuclear factor which is present in rat thymocytes but not splenocytes. These observations suggest that the differential expression of the mouse and rat Thy-1 genes in thymocytes and splenocytes is the result of differential expression of nuclear factors that bind to this 36 bp region.

Role of Thy-1 in T cell development

Tolerance to self proteins is accomplished in part by elimination of autoreactive immature T cells as they develop in the thymus. Although many investigators have studied the cellular interactions that regulate this important process, the specific molecules involved in negative selection are still not well understood. Thy-1 is a glycosyl-phosphatidylinositol-linked protein that is expressed at high levels on immature thymocytes, and recent evidence suggests that it is involved in thymocyte apoptosis. Correspondingly, we have found that Abs to Thy-1 block Ag-dependent thymocyte deletion in an in vitro culture system. Thus, we investigated the role of Thy-1 in T cell development by using Thy-1 -deficient mice containing a TCR transgene specific for a class II MHC-restricted Ag. With this system, the role of Thy-1 in Ag-specific self-restriction and self-tolerance could be analyzed. Thy-1-null mice were found to undergo normal negative selection in three different models: the in vitro culture system, anti-CD3-induced thymocyte deletion in vivo, and Ag-induced thymocyte deletion in vivo. Self-restriction to MHC class II also appeared to occur normally in Thy-1-null mice. These results therefore suggest that Thy-1 is not essential for either self-restriction or self-tolerance to MHC class II-restricted Ags. This finding is discussed in light of recent data regarding the role of other glycosyl-phosphatidylinositol-linked proteins in thymocyte development.

Anti-Thy-1 antibody provokes reverse passive cutaneous anaphylaxis-like reactions

Antibodies to rat Thy-1, and also to murine Thy-1, could provoke reverse passive cutaneous anaphylaxis-like (RPCA-like) reactions. The threshold amount of purified anti-Thy-1 antibodies for RPCA-like reactions was 12.5 microg/ml. No RPCA-like reactions were obtained with IgG1 F(ab')2 anti-Thy-1. Cross-linking the murine anti-rat Thy-1 F(ab')2 fragments with goat antibody against murine F(ab')2 anti-rat Thy-1 permitted us to obtain RPCA-like reactions with as little as 1.5 microg/ ml. However, when the cross-linking was done with the F(ab')2 of the same goat antibody, no RPCA-like reactions were obtained. The antibody against rat FcepsilonRIalpha or its F(ab')2 product were equally effective in producing RPCA-like reactions; the threshold was obtained with 1.5 microg/ml. The mechanism of the difference is discussed.

Differential effect of taurine and serotonin on the outgrowth from explants or isolated cells of the retina

The sulfur amino acid taurine and the indoleamine serotonin increases and decreases, respectively, the outgrowth from goldfish retinal explants. Taurine seems to be acting, at least partially, through an increase in calcium fluxes, and the serotonin-inhibiting effect appears to be mediated by serotonin1A receptors and cAMP. Isolated cells of postcrush goldfish retina and of retina from 5-day-old rats were cultured in the presence of taurine or serotonin. In the goldfish, the classical morphology of postcrush ganglion cells was observed. An antibody against the glycoprotein Thy-1 labelled three types of cells in the cultures of goldfish retina. The number of cells outgrowing and the length of the main neurite was measured at 5 days in culture in both species. The number of cells presenting neurites was increased in the goldfish retina by the addition of taurine, and decreased by serotonin. However, the length of the neurites was unaffected by the addition of the modulators. In the rat, only a slight decrease in the number of cells outgrowing was observed in the presence of serotonin. The incorporation of [3H]thymidine was not modified after 5 days in culture in the presence of taurine or serotonin, either in the goldfish or in the rat retina. The antibody Thy 1.1 can label retinal cells of the goldfish in vitro, one of them being ganglion cells. The trophic effect exerted by taurine in the postcrush goldfish retina needs the integrity of the tissue favoring the interaction of cells and factors, because outgrowth increases in retinal explants, but not in isolated cells.

Thy-1 and AvGp50 signal transduction complex in the avian nervous system: c-Fyn and G alpha i protein association and activation of signalling pathways

We have previously reported the isolation of two distinct populations of detergent resistant membrane complexes (DRMC's) from day-old chick brain (Henke et al.: J Neurosci Res 45:617-630, 1996). We now show that the glycosylphosphatidylinositol-anchored proteins Thy-1 and AvGp50 are associated in a signalling complex with c-Fyn, the heterotrimeric G alpha i subfamily members G alpha i-3, G alpha z, and G alpha o, alpha and beta tubulin, and a number of other phosphoproteins in immunocomplexes isolated from both populations of DRMC's. Activation of this signalling complex via Thy-1 monoclonal antibody incubation with chick forebrain cells, elicited a decrease in total phosphoprotein profile and tyrosine kinase activity present in DRMC fractions isolated from these cells, while AvGp50 and control antibodies had no effect. Down-regulation of the DRMC phosphoprotein profile was accompanied by an increase in the Thy-1-associated signalling complex, suggesting that activation of this complex initiates the decreases seen in overall DRMC kinase activity. This signalling complex provides the basis for GPI-anchored protein-mediated signal transduction within the unique plasma membrane domains represented by DRMC's.

C1q, a subunit of the first component of complement, enhances antibody-mediated apoptosis of cultured rat glomerular mesangial cells

We have shown previously that IgG2a anti-Thy-1 MoAb (ER4G) induces apoptosis of rat mesangial cells (GMC) in vitro. Since the classical complement pathway plays an essential role in Thy-1 nephritis, we analysed whether C1q, a subunit of the first component of complement, enhances the ER4G-mediated apoptosis of rat GMC. Two different subclasses of anti-Thy-1 MoAb, ER4G (IgG2a) and ER14 (IgG1), were used. It was established that ER4G binds C1q efficiently, while ER14 reacts poorly with C1q. For the experiments of apoptosis, quiescent rat GMC were exposed for 1 h at 37 degrees C to a fixed concentration of anti-Thy-1 MoAb and incubated further for 16 h at 37 degrees C in the presence or absence of C1q. GMC exposed to medium (M-GMC) followed by incubation of the cells with medium alone was used as controls. Apoptosis was assessed by morphological studies and quantitative analysis on FACS using FITC-annexin V (the annexin V methods) or bicolour FACS analysis using FITC-annexin V and propidium iodide (the annexin V/PI method). With the annexin V method, M-GMC revealed 9.4 +/- 1.4% apoptosis. C1q had only marginal effects on apoptosis of M-GMC. GMC exposed to ER4G (ER4G-GMC) and further incubated with medium in the absence of C1q resulted in 25.7 +/- 5.7% apoptosis (P < 0.01 relative to control). Incubation of ER4G-GMC together with 100 microg/ml of C1q significantly increased GMC-apoptosis up to 39.4 +/- 4.9% (P < 0.01 relative to ER4G-GMC incubated in the absence of C1q). This enhancing effect of C1q on apoptosis of ER4G-GMC was time- and dose-dependent. In contrast, C1q did not significantly alter the apoptosis of either GMC exposed to ER14 (ER14-GMC) or to F(ab')2-ER4G (F(ab')2-ER4G-GMC), while ER14-GMC or F(ab')2-ER4G-GMC incubated with medium resulted in significant apoptosis compared with control. These results were supported by morphological studies and bicolour FACS analyses in time course experiments using the annexin V/PI method. The effect of C1q is dependent on the presence of intact C1q-containing globular heads and does not occur with collagen-like fragments of C1q. Furthermore, incubation of ER4G-GMC with anti-mouse K-chain antibodies also increased ER4G-mediated GMC-apoptosis. These results indicate for the first time that C1q enhances antibody-mediated apoptosis of rat GMC in vitro, presumably by its binding to ER4G and probably by additional cross-linking of Thy-1 on the surface of GMC.

Nonatopic asthma: in vivo airway hyperreactivity adoptively transferred to naive mice by THY-1(+) and B220(+) antigen-specific cells that lack surface expression of CD3

To investigate the cellular immune events contributing to airway hyperreactivity (AHR), we studied an in vivo mouse model induced by the hapten picryl (trinitrophenyl) chloride (PCl). Mice were immunized by cutaneous contact sensitization with PCl and airway challenged subsequently with picryl sulfonic acid (PSA) antigen (Ag). Increased airway resistance was produced late (24 h) after Ag challenge, disappeared by 48 h, and was associated with no decrease in diffusion capacity. AHR could be produced in PCl immune/ PSA challenged mice on day 7 or even, with challenge, as early as 1 d after contact sensitization, after adoptive transfer of immune cells lacking CD3(+) contact sensitivity effector T cells, or after transfer of Ag-specific lymphoid cells depleted of conventional T lymphocytes with surface determinants for CD3, CD4, CD8, TCR-beta, or TCR-delta molecules. Further experiments showed that development of AHR depended upon transfer of immune cells expressing surface membrane Thy-1 and B220 (CD45RA) determinants. We concluded that a novel population of Ag-specific lymphoid cells with a defined surface phenotype (Thy-1(+), CD3(-), CD4(-), CD8(-), TCR-alphabeta-, TCR-gammadelta-, and CD45RA+) is required in a mouse model for the development of AHR.

Expression of blood-brain barrier characteristics following neuronal loss and astroglial damage after administration of anti-Thy-1 immunotoxin

In most regions of the CNS, vascular endothelial cells play an important role in maintaining the composition of the neuronal microenvironment by virtue of their blood-brain barrier (BBB) characteristics. The maintenance of the endothelial BBB phenotype in vitro has been attributed primarily to astrocytes but little attention has been paid the potential role of neurons. In this study we have attempted to injure or destroy neurons and fibers of passage in a circumscribed area while leaving vascular and glial elements intact in order to determine if neurons are involved in BBB maintenance in situ. The immunotoxin OX7-SAP, a conjugate of the Thy-1 antibody OX7 and the ribosome-inactivating protein saporin, was injected into the adult rat striatum to effect neuronal death at the injection site. Although neurons and fibers of passage were destroyed within the lesion, glial cells unexpectedly were also severely injured as determined by immunohistochemical expression of several neuronal and astroglial marker proteins and ultrastructural analysis. The microvasculature remained intact, allowing a qualitative immunohistochemical analysis of several BBB markers at time points ranging from 3 to 28 days postinjection. Despite the loss of both neurons and astroglia within the lesions, the microvasculature continued to express the brain-type endothelial glucose transporter GLUT-1 at all time points examined. In contrast, the barrier to endogenous protein (rat serum albumin) and the expression of endothelial barrier antigen (EBA) decreased initially but recovered even in areas that contained minimal numbers of astroglia and neuronal elements. We conclude that intact neuronal or glial cells do not appear to be necessary for the maintenance in situ of the BBB properties examined herein.

Role of interleukin-1 in mesangial cell proliferation and matrix deposition in experimental mesangioproliferative nephritis

We examined the functional role of interleukin (IL)-1 in mesangial cell proliferation during rat anti-Thy-1 nephritis by blocking its action with IL-1 receptor antagonist (IL-1ra). Anti-Thy-1 nephritis was induced by intravenous injection of 5 mg/kg OX-7 IgG (day 0) into inbred Wistar rats. Groups of animals (n = 9) were implanted with a micro-osmotic pump on day -1, which delivered 25 micrograms/hour human recombinant IL-1ra or saline continuously until the rats were killed at day 6, the peak of mesangial cell proliferation. Immunostaining showed that IL-1 was expressed by mesangial cells during disease. IL-1ra treatment did not affect the mild, but significant, proteinuria seen after OX-7 injection. Compared with saline treatment, IL-1ra treatment reduced mesangial cell proliferation (decreases 24% P < 0.05), glomerular hypercellularity (decreases 29%; P < 0.05), and glomerular macrophage accumulation (decreases 20%; P < 0.05). However, IL-1ra treatment had no effect on glomerular IL-1 beta mRNA expression and caused only a small reduction in the high levels of glomerular expression of platelet-derived growth factor-beta protein (decreases 6%; P < 0.05). IL-1ra caused a modest reduction in the marked up-regulation of glomerular transforming growth factor-beta 1 mRNA expression on day 6 (decreases 26%; P < 0.05), although urinary excretion of this factor was unaffected. Interestingly, IL-1ra treatment had relatively little effect upon glomerular deposition of laminin, fibronectin, and collagen type IV seen in this acute disease. In conclusion, this study has 1) demonstrated that IL-1 is expressed by mesangial cells in vivo, 2) demonstrated that IL-1 is a mesangial cell growth factor in experimental mesangioproliferative nephritis, and 3) suggests that IL-1 has little or no fibrogenic activity in mesangial matrix deposition.

Selective ablation of rat knee joint innervation with injected immunotoxin: a potential new model for the study of neuropathic arthritis

Neuropathic arthropathy is a severe chronic degenerative condition associated with decreased or absent sensory innervation of the involved joint. Existing animal models of neuropathic arthritis are limited by the technical difficulties of obtaining either highly selective or complete joint denervation in a minimally invasive fashion. We undertook experiments to determine the feasibility of using the newly described method of selective neuronal lesioning with injected immunotoxin as a means of creating a more tractable model of neuropathic arthritis. Retrograde tracing with fluorochrome revealed that the knee joint of the female Wistar rat is supplied by 581 +/- 31 (mean +/- SD) joint afferents. Immunohistochemistry confirmed that virtually all sensory neurons in the rat express the cell surface receptor Thy 1. Injection of rat knee joints with an immunotoxin targeted toward Thy 1 resulted in the selective ablation of an average of 88% of the joint afferents identified with fluorochrome that are normally found in the ipsilateral L3 and L4 ganglia.

Extrahepatic C6 is as effective as hepatic C6 in the generation of renal C5b-9 complexes

In order to study the contribution of extrahepatic C6 to anti-Thy1.1 nephritis, C6 deficient PVG/c- livers were grafted in C6 sufficient PVG/c+ rats (Tx-L). Infusion of anti-Thy1.1 antibodies in Tx-L and PVG/c+ rats resulted in generation of C5b-9 complexes and subsequent glomerular injury, while infusion of anti-Thy1.1 antibodies in PVG/c- rats revealed no detectable C6 deposition. Because C6 mRNA was expressed in both liver and kidney tissue of PVG/c+ rats, we assessed whether production of C6 in the kidney alone was sufficient for glomerular injury. One kidney of a PVG/c- rat was replaced with a PVG/c+ kidney (Tx + K) followed by administration of anti-Thy1.1 antibodies. C6 deposits were detectable neither in PVG/c+ kidneys nor in PVG/c- kidneys of Tx + K rats, indicating that C6 production in PVG/c+ kidneys alone is not sufficient to contribute to renal injury. That C6 production had occurred was suggested by the presence of equal amounts C6 mRNA in control PVG/c+ kidneys and in grafted PVG/c+ kidneys of Tx + K rats. C6 mRNA expression in kidney tissue of PVG/c+ rats is presumably derived from peritubular sites. In conclusion, we have demonstrated that extrahepatic, but not renal synthesis of, C6 is sufficient to contribute to glomerular injury during anti-Thy1.1 nephritis.

Anti-angiogenic compound (TNP-470) inhibits mesangial cell proliferation in vitro and in vivo

Growth factors, especially basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and transforming growth factor-beta (TGF-beta) are known to play key roles in the pathogenesis of mesangial proliferative glomerulonephritis. TNP-470 (AGM-1470), a potent anti-angiogenic compound, has anti-growth factor properties and inhibits the activation of cyclin-dependent kinase (cdk) 2 and phosphorylation of RB protein. We investigated whether TNP-470 could suppress growth factor induced mesangial cell proliferation in vitro and experimental model of mesangial proliferative glomerulonephritis in vivo. TNP-470 inhibited potently PDGF- and bFGF-stimulated proliferation of rat mesangial cells in vitro (IC50 = 50 pg/ml). In anti-Thy 1.1 glomerulonephritis, high dose use of TNP-470 (20 mg/kg/day) markedly suppressed mesangial cell proliferation and mesangial matrix expansion on day 6; however, mesangiolysis remained. Low dose use of TNP-470 (10 mg/kg/day) moderately inhibited mesangial cell proliferation and mesangial matrix synthesis, and induced appropriate glomerular healing on day 14 in anti-Thy 1.1 glomerulonephritis. Thus, TNP-470 potently inhibits growth factor-induced proliferation of mesangial cells in vitro, and mesangial cell proliferation and extracellular matrix expansion in anti-Thy 1.1 glomerulonephritis in vivo. These results suggest a novel therapeutic potential of TNP-470 in mesangial proliferative glomerulonephritis.

Decrease in Thy-1 expression on peripheral CD34 positive cells induced by G-CSF mobilization. The Tohoku Children Leukemia Study Group

In order to ascertain the cytological features of peripheral hematopoietic progenitor cells (PHPC) mobilized after administration of chemotherapeutic agents and G-CSF, lineage- and progenitor cell-specific surface markers on CD34 positive (+) cells were sequentially examined. Nineteen evaluable samples were obtained from a malignant lymphoma, an acute lymphoblastic leukemia and 5 neuroblastoma patients. CD38 and HLA-DR were respectively expressed on more than 95% and approximately 85% of CD34+ PHPC cells. CD19 was also expressed on the majority and CD117 on 10 to 20% of the CD34+ cells. The most striking finding was that the Thy-1(CDw90)+/CD34+ population was decreased at the peak of mobilization of CD34+ cells as compared to the early phase after G-CSF administration (approximately 20% vs. 60%). These results suggest that decrease in Thy-1 expression on CD34+ cells is related to mechanisms easing CD34+ cell mobilization to the peripheral blood.

Aggregation of Thy-1 glycoprotein induces thymocyte apoptosis through activation of CPP32-like proteases

Mouse thymocytes are known to undergo apoptosis by ligating some unique anti-Thy-1 monoclonal antibodies (mAbs), G7 and KT16. However, the precise mechanisms of Thy-1-mediated apoptosis are as yet unclear. We investigated Thy-1-mediated apoptosis using our previously generated anti-Thy-1 mAb, MCS-34, which was similar to G7 because both antibodies recognized both Thy-1.1 and Thy-1.2 and bound Thy-1A epitope. Unlike G7, MCS-34 alone could not induce apoptosis in thymocytes; however, it could induce apoptosis when it was cross-linked with second antibodies. Thus, MCS-34 could not aggregate by itself, but G7 could. In the course of investigating the apoptosis-related molecules that were involved in the thymocyte apoptosis induced by cross-linking of MCS-34 or by G7 ligation, we found that CPP 32-like proteases were activated during the apoptosis. Furthermore, the expression of bcl-2 and bcl-XL proteins was decreased in these apoptosis processes. Whereas the ligation of MCS-34 alone could not generate apoptosis signals that led to the activation of CPP32-like proteases and the decrease in bcl-2 and bcl-XL expression, the aggregation of Thy-1 glycoprotein might be crucial to signal thymocyte apoptosis. These results indicate that MCS-34 is a useful anti-Thy-1 mAb for analyzing the Thy-1-mediated signals since MCS-34 can control the level of apoptosis by using second antibodies.

[Heterogeneity of pulmonary fibroblasts in tuberculosis]

Chronic inflammation and pneumofibrosis are the central events in tuberculosis morphogenesis. It was suggested that a certain type of fibroblasts may play a role in chronization of the inflammation and development of sclerosis in tuberculosis. Fibrous tissue from the foci of secondary tuberculosis (fibrous-cavernous tuberculosis and tuberculomas) of 35 patients were studied light- and electron-microscopically and immunohistochemically. (THY 1-)fibroblasts non-containing lipids and producing insulin-like growth factor 2 (ILGF 2), binding proteins 2 and 4 and epidermal growth factor receptors were found in the foci of secondary tuberculosis close to the granulomatous inflammation and in the new and scarrous fibrous connective tissue of the tuberculoma capsule and caverna walls. These fibroblasts are able for auto- and paracrine regulation of the proliferation of fibroblasts, epithelium and other cells in the inflammatory foci. (THY 1+) fibroblasts containing lipids were observed in the foci of old sclerotic changes among the rough collagen fibres. Thus, (THY 1-) fibroblasts probably play a key role in chronization of inflammation, proliferation and pretumorous dysplasia of pulmonary epithelium in secondary tuberculosis. (THY 1+) fibroblasts containing lipids may show more pronounced collagenesis and may persist under hypoxia condition in the collagenous scars for a long time.

Specific tolerance induction and transplantation: a single-day protocol

Bone marrow transfusion is a well-established method for induction of mixed hematopoietic chimerism and donor-specific tolerance in animal models. This procedure, however, is inapplicable in clinical transplantation using cadaveric donors due to the interval (1 week to 7 months) between tolerance induction and organ transplantation. For clinical use, it is essential that allografts be placed at the time of bone marrow transfusion. In the present study, we performed skin transplantation within 1 hour after a nonlethal conditioning regimen. Recipient mice were treated with anti-CD3, anti-CD4, low-dose total body irradiation (3 to 6 Gy TBI) and fully mismatched or haploidentical donor bone marrow cells. Stable multilineage chimerism and specific T-cell nonresponsiveness developed. Donor skin grafts were permanently accepted. These results suggest that this single day protocol has clear potential for application in both cadaveric and living-related organ transplantation.

Thy-3, a developmentally regulated T-cell glycoprotein associated to Thy-1 in detergent-resistant membrane microdomains

The function of the Thy-1 molecule, a major T-cell glycoprotein, is still obscure. Its functional properties might be due to the anchoring via a glycosylphosphatidylinositol group which favors gathering of molecules in functional membrane subregions called microdomains. Using novel monoclonal antibodies, we describe a 53-kDa Thy-1-associated glycoprotein called Thy-3. Thy-3 expression is restricted to T lymphocytes, becomes detectable on double-positive thymocytes, and depends on that of Thy-1. Anti-Thy-3 antibodies immunoprecipitate Thy-1 and Thy-3 or Thy-3 alone in detergents which preserve or disrupt microdomains, respectively. These antibodies induce thymocyte aggregation and interfere with adhesion of thymocytes to a thymic epithelial cell line as previously shown with anti-Thy-1 antibodies. Thus, Thy-3 is a T lineage-specific glycoprotein associated to Thy-1 in membrane microdomains and might contribute to the function of Thy-1 in T-cell differentiation.

Role of interleukin-6 in mediating mesangial cell proliferation and matrix production in vivo

Mesangial cell proliferation and matrix overproduction characterize many progressive glomerular diseases. Based on currently available data, the role of interleukin-6 (IL-6) in mediating mesangial cell proliferation and matrix production is controversial. The present study attempts to clarify this issue by showing that: (1) IL-6 knock out mice develop a normal glomerular architecture and in particular a normal mesangium. (2) Mesangioproliferative glomerulonephritis induced by Habu snake venom is equally severe in IL-6 knock out mice as in control mice. (3) A continuous seven-day intraperitoneal infusion of 50 micrograms recombinant human IL-6 into rats with a prior minimal (subnephritogenic) injury to mesangial cells does not induce glomerular cell activation, cell proliferation, matrix production, leukocyte influx, platelet influx or proteinuria. (4) A continuous seven-day IL-6 infusion into rats with mesangioproliferative nephritis (anti-Thy 1.1 nephritis) increases matrix protein transcription in the absence of detectable effects on matrix protein accumulation and otherwise has no effect on the natural course of the disease. We conclude from these findings that IL-6 is not an important mediator of mesangial cell proliferation and matrix overproduction in vivo, and that currently little rationale exists to advocate anti-IL-6 therapy in mesangioproliferative disease states.

Two distinct populations of primary cytotoxic cells infiltrating into allografted tumor rejection sites: infiltration of macrophages cytotoxic against allografted tumor precedes that of multiple sets of cytotoxic T lymphocytes with distinct specificity to alloantigens

It has been reported that the rejection of tumor allografts is mainly mediated by cytotoxic T lymphocytes (CTLs). Here, we characterized the cytotoxic effector cells of C57BL/6 (B6; H-2b) mice infiltrating into the rejection site of the i.p. allografted Meth A fibrosarcoma (or P815 mastocytoma) cells of H-2d origin. Two types of cytotoxic cells (i.e., CD8+ CTLs and macrophages (M phi s)) were identified by flow cytometric fractionation of the infiltrates or by specific in vitro elimination of cells either with antibody (Ab)-coated beads or with an Ab-plus complement. Of particular interest, these effector cells showed distinct and unique target specificities. First, the CTLs were inactive against transplanted tumor (e.g., Meth A) cells, whereas they were cytotoxic against donor-related concanavalin A (Con A) blasts as well as CTLL-2 (H-2b) cells transfected with a class I gene of H-2d origin. A cold target competition assay suggested that the CTLs were composed of multiple sets of T cells, each of which specifically recognized different allo-antigens. Second, the M phi s lysed the allografted tumor cells but were inert toward the Con A blasts and the CTLL-2 transfectants. Unexpectedly, the infiltration of M phi s preceded the infiltration of CTLs by several days during the course of rejection. These results indicate that two distinct populations of unique cytotoxic cells (i.e., CTLs and M phi s) are induced in the allografted tumor rejection site, and that the infiltration of cytotoxic M phi s responsible for rejection precedes that of the CTLs cytotoxic against cells expressing donor-related allo-antigens.

Efficient induction of apoptosis in cultured rat glomerular mesangial cells by dimeric monoclonal IgA anti-Thy-1 antibodies

Apoptosis of glomerular cells (GMC) has been observed in the early phase as well as the resolution phase of Thy-1 nephritis. Recently, we and others reported that IgG2a (ER4G) and IgG1 (OX7) monoclonal mouse anti-Thy-1 antibodies (anti-Thy-1 MoAb) are able to induce apoptosis of rat GMC in vivo. The purpose of this study was to investigate whether cross-linking of Thy-1 would influence the degree of apoptosis in cultured rat GMC using monomeric and dimeric IgA anti-Thy-1 MoAb. IgA anti-Thy-1 MoAb (ER4A) was generated by class switching of the IgG producing ER4 (ER4G) hybridoma. The ER4A clone spontaneously produces monomeric (m-ER4A) and dimeric IgA anti-Thy-1 MoAb *di-ER4A). Unaltered epitope specificity of ER4A was confirmed by blocking experiments of the binding of fluorescence labeled ER4G to cultured rat GMC with unlabeled ER4A on FACS. For the experiments of apoptosis, quiescent rat GMC were incubated for eight hours with medium alone or with medium in the presence of 10 micrograms/ml of m-ER4A, di-ER4A or control IgA MoAb of corresponding sizes. Apoptosis was assessed by morphological studies, agarose gel electrophoresis and quantitative FACS analyses using terminal deoxynucleotidyl transferase (TDT) method and the annexin V method. The TDT method detects specific-DNA nicking in apoptosis. The annexin V method detects early membrane changes during apoptosis. In morphological studies, cells incubated with m-ER4A and di-ER4A showed typical apoptotic features such as nuclear condensation and fragmentation. DNA isolated from the cells incubated with di-ER4A was cleaved into a distinctive ladder pattern compatible with apoptosis. In contrast, both medium alone and control IgA MoAb did not reveal detectable changes in morphological studies and agarose gel electrophoresis. In quantitative analyses by FACS using the TDT method and the annexin method, both m-ER4A and di-ER4A induced significantly higher percentages of apoptosis in rat GMC as compared to the controls. Furthermore, di-ER4A was considerably more efficient than m-ER4A in inducing apoptosis possibly through additional cross-linking of Thy-1 on the cell surface. This notion was confirmed by experiments, in which the addition of goat anti-mouse kappa antibodies enhanced apoptosis of rat GMC pre-sensitized with m-ER4A. Taken together, our results indicate that apoptosis of rat GMC by anti-Thy-1 antibodies is enhanced by cross-linking of Thy-1 on the cell surface. These studies are of importance for our understanding of mechanisms that may play a role in glomerular diseases.

Autoregulation of total and zonal glomerular filtration rate in spontaneously hypertensive rats with mesangiolysis

In this study we tested the hypothesis that mesangial cells participate in autoregulation of the glomerular filtration rate (GFR) in normotensive and hypertensive rats. Mesangial cell lesions were induced by intravenous administration of antithymocyte (anti-Thy 1.1) antibodies in spontaneously hypertensive rats (SHR) and in Wistar-Kyoto rats (WKY). Normal murine serum was injected in control rats. Hemodynamic measurements were performed 24 h after the infusion of the anti-Thy 1.1 antibodies. Renal blood flow (RBF) was measured by a transit time flowmeter (Transonic) and the GFR was measured as the uptake of 125 iodine-labeled aprotinin ([125]I-Ap) by proximal tubular cells at the control renal arterial pressure and (131)I-Ap at a pressure reduction close to the lower pressure limit of RBF autoregulation. RBF was unaltered and the autoregulatory capability was maintained in SHR and WKY after mesangial cell lesions. Mesangiolysis significantly reduced the total GFR in normotensive, but not in hypertensive animals. The fractional compensation of the GFR was attenuated in the outer cortical layer (p<0.05) in normotensive WKY. In SHRs the fractional compensation of the GFR was impaired in all cortical layers after mesangiolysis, slightly more in the outer than in the inner cortex. We conclude that mesangial cells may contribute to the autoregulation of GFR in hypertensive rats, but to a lesser extent in normotensive rats.

In vivo effect of OPC15161, a superoxide scavenger, on anti-Thy1 nephritis

The in vivo effect of 6-(1 H-indol-3-ylmethyl)-5-methoxy-3-(2-methylpropyl)-2(1 H)-pyrazinone, 4-oxide (OPC15161), a superoxide scavenger, was studied in rats with anti-Thy1 nephritis. Rats were divided into 4 groups: G-1, normal control; G-2, anti-Thy1 nephritis; G-3 anti-Thy1 nephritis and treated with OPC15161 (50 mg/kg/day) starting at day 0; and G-4, anti-Thy1 nephritis and treated with OPC15161 starting 3 days before antibody injection. At weeks 2 and 8, rats were killed for morphological study and at week 8 for renal clearance. Results were compared among the 4 groups. OPC15161 suppressed urinary albumin/day. Total glomerular cells, mesangial cells, ED-1-positive cells/glomerulus and glomerular volume all increased and the increases were suppressed by OPC15161. Tubulointerstitial index, assessed by point counting, was improved by OPC15161 (P < 0.05 G-3, 4, vs. G-2, not significant vs. G-1). Glomerular filtration rate decreased in all nephritic animals, but the decrease in renal blood flow was less in the treated groups. These findings indicate a favorable effect of OPC15161 on the glomerular and interstitial lesions of anti-Thy1 nephritis.

Induction of microhematuria by an IgA isotype switch variant of a monoclonal anti-Thy-1.1 antibody in the rat

IgA nephropathy (IgAN) is a chronic form of glomerulonephritis (GN) characterized by the deposition in the glomerular mesangium of mainly IgA. An experimental form of mesangial proliferative GN can be induced in rats by either polyclonal or monoclonal antibodies against Thy-1.1, a glycoprotein present on the surface of MC. The IgG-mediated renal inflammation is complement dependent and associated with influx of platelets and monocytes. In the present study we switched an IgG2a anti-Thy-1.1 (ER4G) producing hybridoma to an IgA anti-Thy-1.1 (ER4A) producing clone and analyzed the effects of IgA anti-Thy-1.1 in rats. FPLC analysis by gel filtration revealed that the IgA produced by the hybridoma cells was mainly dimeric and polymeric. Infusion of rats with purified ER4A (1 mg/kg) resulted in the deposition of IgA in a mesangial pattern in the glomeruli, similar to that found with ER4G. While administration of ER4G resulted in proteinuria, no significant urinary protein excretion was found in rats treated with ER4A. However, significant microhematuria was observed in rats receiving either ER4A or ER4G. Furthermore, the administration of ER4A was not accompanied by activation of complement, and no significant influx of monocytes or polymorphonuclear leukocytes was observed in contrast to the rats receiving ER4G. We conclude that microhematuria is selectively induced in Wistar rats by mouse IgA anti-Thy-1.1 without detectable complement-mediated injury to MC. These studies may be of importance in understanding the mechanisms leading to IgAN in patients.

Thy-1 molecule associates with protein tyrosine kinase(s) in rat mesangial cells

Glycophosphatidylinositol (GPI)-linked Thy-1 molecules, well known cell surface markers of murine T cells, are present on the glomerular mesangial cells of the rat kidney. The administration of anti-Thy-1.1 MoAbs 1-22-3 and OX-7 to rats induces severe and mild complement-dependent mesangial proliferative glomerulonephritis, respectively. In order to determine whether protein-tyrosine kinase (PTK) activity is associated with Thy-1 molecules on rat mesangial cell surface, we performed an immune complex kinase assay, using anti-Thy-1 MoAbs 1-22-3 and OX-7, followed by reimmunoprecipitation with anti-phosphotyrosine, anti-fyn, anti-lck and anti-lyn antibodies. Physical association of PTK, p59fyn and p56/53lyn with Thy-1 molecules was demonstrated in cultured rat mesangial cells. The activities of these kinases detected in MoAb 1-22-3 precipitates were higher than those in MoAb OX-7 precipitates. These results suggest that Thy-1 molecule transduces some signals also in rat mesangial cells.

T helper cells in murine germinal centers are antigen-specific emigrants that downregulate Thy-1

After immunization, activated splenic T cells proliferate in periarteriolar lymphoid sheaths (PALS) and subsequently migrate to the lymphoid follicle where they enter nascent germinal centers. Analysis of TCR V(D)J gene rearrangements indicates extensive emigration, frequently involving more than a single white pulp region. These migrants constitute a unique set of T helper cells that express antigen-specific alpha beta TCR, CD3, and CD4, but little or no Thy-1, a differentiation antigen present on the great majority of peripheral murine T lymphocytes. The origin of CD4+ Thy-1 follicular T cells appears to be the Thy+ population in the PALS, as both sets commonly share identical V(D)J rearrangements.

Fas system-mediated apoptosis suppresses lymphopoiesis

The lymphoproliferation (lpr) mutation causes the defective expression of Fas Ag, which normally transduces an apoptotic signal into cells. T cells from mice homozygous for this mutation overexpress the counter-receptor, Fas ligand. In this study, we investigated the effects and regulatory influences attributable to Fas ligand overexpression on lymphocyte development to clarify the role of Fas system-mediated apoptosis in lymphopoiesis in vivo. Nonirradiated severe combined immunodeficient (SCID) mice grafted with a fetal thymus (FT) plus fetal liver cells (FLC) from MRL-lpr/lpr mice (Fas Ag-defective mice), or with FT from C3H-gld/gld mice (Fas ligand-defective mice) plus FLC from C3H +/+ mice, developed FLC-derived T and B cells. In contrast, SCID mice grafted with FT from MRL-lpr/lpr Thy-1.1 mice plus FLC from MRL +/+ Thy-1.2 mice (chimera 1) developed few FLC-derived T and B cells in the spleen, and the thymus of the recipients also contained few FLC-derived T cells. In addition, when SCID mice grafted with FT from MRL-lpr/lpr Thy-1.2 mice (H-2k) were co-transplanted with FLC from C57BL/10 Thy-1.1 mice (H-2b) (chimera 2), FLC-derived T and B cells developed normally. Thy-1.1 + cells from chimera 1 expressed Fas ligand mRNA about threefold higher than those from chimera 2, and seven- to eightfold higher than Thy-1.2+ cells from SCID mice grafted with FT from MRL +/+ Thy-1.2 mice by Northern blot analysis. These findings indicate that overexpression of Fas ligand on T cells significantly impairs both T and B cell development. Furthermore, the Fas ligand overexpression sufficient to impair lymphopoiesis appears to require MHC-restricted T cell activation. These results suggest that the Fas system suppresses lymphopoiesis in vivo.

ICAM-1-, -2- and LFA-1-independent homotypic T cell aggregation induced by a novel activating monoclonal antibody targeting the murine Thy-1 molecule

We have previously reported that the murine T cell line EL-4 has an aggregating phenotype, displaying homotypic aggregation (HTA) when exposed to monoclonal antibodies targeting specific cell surface molecules such as leukocyte function-associated antigen-I (LFA-1). We have used this property of EL-4 cells to isolate additional HTA-inducing MAb by screening a panel of hybridomas that were generated from rats immunized with EL-4 cells. We have isolated a novel anti-Thy-1 MAb (termed FF-10) that is a powerful inducer of HTA in EL-4 cells. In addition to induction of HTA, FF-10 also induces splenocyte proliferation but inhibits anti-CD3-driven T cell proliferation. Thy-1-induced HTA cannot be blocked with MAb targeting intercellular adhesion molecule-I and -2 (ICAM-1, ICAM-2) or LFA-1. Thus, the FF-10 MAb represents a novel and unique tool to investigate the diverse roles of the murine Thy-I molecule in T cell activation, proliferation and apoptosis.

De novo CD44 expression by proliferating mesangial cells in rat anti-Thy-1 nephritis

CD44 is the major cell-surface receptor for hyaluronan, and cell-matrix interactions mediated by the CD44/hyaluronan receptor-ligand pair are involved in a variety of cellular functions, including cell migration. The aim of the study presented here was to examine the expression of CD44 and hyaluronan in the mesangial proliferative response in rat anti-Thy-1 nephritis. In normal rat kidney, CD44 is expressed by medullary tubules, some distal tubules and thick ascending limbs of Henle, dendritic-like cells around Bowman's capsule, and some interstitial cells. However, only occasional CD44+ cells were found within the glomerular tuft. In experimental nephritis, there was an early glomerular influx of CD44+ macrophages, which peaked on Day 4 after anti-Thy-1 antibody injection. A striking finding was de novo CD44 expression by mesangial cells. This CD44 expression was restricted to the transient period of mesangial cell proliferation as shown by double-staining with an antibody against the proliferating cell nuclear antigen. Immunohistochemistry staining also demonstrated hyaluronan deposition within segmental areas of proliferating CD44+ cells, suggesting a functional interaction between the CD44/hyaluronan receptor-ligand pair during mesangial cell proliferation. In vitro, rat mesangial cells were shown to express mRNA and protein for the 90-kd isoform of CD44. In addition, hyaluronan-dependent aggregation of CD44+ mesangial cells was specifically inhibited by an anti-CD44 antibody, demonstrating a functional interaction between hyaluronan and the CD44 expressed on the surface of rat mesangial cells. In conclusion, these data suggest that cell-matrix interactions mediated by the CD44/hyaluronan receptor-ligand pair are involved in mesangial cell proliferation in rat anti-Thy-1 nephritis.

The cytoskeletal linking proteins, moesin and radixin, are upregulated by platelet-derived growth factor, but not basic fibroblast growth factor in experimental mesangial proliferative glomerulonephritis

The expression of the two cytoskeletal linking proteins, moesin and radixin, was examined in experimental mesangial proliferative nephritis in rats (anti-Thy1 model). Moesin and radixin mRNA and protein are constitutively expressed in all cell types of normal rat glomeruli, except podocytes. In the anti-Thy1 model the expression of moesin and radixin was increased in infiltrating macrophages and in activated, alpha-smooth muscle actin-positive mesangial cells and was concentrated in the cellular extensions of mesangial cells in areas of glomerular remodelling. Studies using neutralizing antibodies demonstrated that the increase in moesin and radixin expression by mesangial cells is mediated by PDGF, but not bFGF. The increase in these cytoskeletal proteins appears to be regulated primarily (radixin) or partially (moesin) posttranscriptionally. The data suggest that PDGF mediated upregulation of the cytoskeletal proteins, moesin and radixin, is important for cell migration and other changes that accompany the coordinated restoration of glomerular architecture after injury.

A novel anti-Thy-1 (CD90) monoclonal antibody induces apoptosis in mouse malignant T-lymphoma cells in spite of inducing bcl-2 expression

Mouse malignant T-lymphoma CS-21 cells can survive and proliferate in vitro when co-cultured with CA-12 stromal cells isolated from lymph nodes, but CS-21 cells undergo apoptotic cell death with DNA fragmentation when cultured alone. We immunized rats with CS-21 cells and raised monoclonal antibodies (MAbs) that recognized Thy-1 (CD90) or CD45 protein. The majority of these MAbs were able to inhibit the adhesion and apoptosis of CS-21 cells. When anti-Thy-1 MAbs were examined for their recognition site on Thy-1 glycoprotein, one of them, MCS-34, was found to recognize both Thy-1.1 and Thy-1.2. In addition, MCS-34, just like the anti-Thy-1 MAb G7, recognized the Thy-1A epitope. G7 was known to induce apoptosis in some T-cell hybridomas and in thymocytes. In CS-21 cells, however, G7 could not induce apoptosis, but MCS-34 could. Interestingly, MCS-34 enhanced the expression of bcl-2 protein, in spite of its ability to induce apoptosis. Upon examining the apoptosis-inducing mechanisms of MCS-34, we found that it promoted a sustained increase in cytoplasmic-free calcium in CS-21 cells. Calcium ionophore A23187 was also found to induce apoptosis in a dose-dependent manner. These results indicate that a sustained increase in cytoplasmic-free calcium by MCS-34 induces apoptosis in CS-21 cells in spite of bcl-2 protein expression.

Effect of acteoside on mesangial proliferation in rat anti-Thy 1 nephritis

We investigated whether acteoside can inhibit mesangial matrix expansion or mesangial cell proliferation in mesangioproliferative anti-Thy 1 nephritis. Untreated control rats were compared to the rats treated with acteoside either during early (day 1 to 8) or late (day 4 to 12) period after the induction of anti-Thy 1 nephritis. The result showed that acteoside and prednisolone treatments (in either early or late period) significantly reduced proteinuria, mesangial matrix expansion (the index of matrix expansion) and mesangial proliferation as determined by the number of proliferating nuclear cell antigen (PCNA)-positive cells. Acteoside also reduced glomerular macrophage infiltration and ICAM-1 expression in glomeruli of anti-Thy 1 nephritic rats. Furthermore, acteoside treatment markedly increased the activities of matrix metaloproteinases (MMP) in glomeruli. These results suggest that acteoside can inhibit mesangial cell proliferation and extracellular matrix overproduction by either inhibiting ICAM-1 expression or increasing activities of MMP.