Human anti-streptokinase antibodies induce platelet aggregation in an Fc receptor (CD32) dependent manner

Exposure to streptokinase (SK) elicits anti-SK antibodies (Abs), which inhibit fibrinolysis and induce platelet aggregation. The mechanism of the latter is not fully understood, although it seems to involve platelet binding by a plasminogen streptokinase and anti-SK ternary complex. Anti-SK Abs were purified by affinity chromatography from serum of patients having received SK for acute myocardial infarction (AMI), and were shown to be of the IgG type. Their effects were studied with (i) human platelets in citrated plasma in the presence of SK or acetylated plasminogen-SK activator complex (APSAC), and (ii) in washed platelets, resuspended in Tyrode buffer after lowering the ionic strength, in the presence of APSAC (which provides both SK and plasminogen). An antibody concentration-response curve was obtained, showing a plateau in the presence of 0.1 mg/ml IgG. By increasing the concentration of APSAC, we obtained a unimodal response curve, the optimal concentration of APSAC being 0.05 U/ml. Aggregation was suppressed by chelating calcium with EDTA, blocking fibrinogen binding by the synthetic peptide Arg-Gly-Asp-Ser (RGDS), and raising intraplatelet cAMP with Iloprost (a prostacyclin analogue). Aggregation required the interaction of the anti-SK Ab Fc domain with the platelet Fc-gamma receptor type II, also known as CD32, since: (i) it was blocked by the monoclonal antibody IV-3 directed against CD32, (ii) it did not occur with F(ab)'2 fragments, which block the response to the intact IgG. The clinical relevance of these platelet-activating anti-SK antibodies remains to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of elastase and fibrin in venous leg ulcer biopsies: a pilot study of pentoxifylline versus placebo

The pathogenesis of venous leg ulcers is based on the leakage of fibrinogen leading to a pericapillary fibrin cuff and plugging of capillaries by white blood cells. On the basis of a previous work, we had assumed that the key event in the pathogenesis of venous leg ulcers is related to inflammation generated by activated white blood cells that accumulate under unrelieved blood pressure, because in ulcer biopsies we had detected the presence of tumor necrosis factor-alpha (TNF-alpha) in intracapillary monocytes, elastase in the polymorphonuclear leukocytes near the vessels, and a pericapillary undegraded fibrin cuff causing a diffusion barrier to oxygen. This concept was developed because TNF-alpha synthesized by activated monocytes is responsible for many deleterious effects. It has a potent mitogenic effect on fibroblasts, leading to new collagen deposition and angiogenesis, it induces an increase in collagenase production, it acts through upregulation of an intracellular adhesion molecule (ICAM-1), leading to leukocyte sequestration and consequently a release of toxic metabolites by the polymorphonuclear cells, an early step in chronic inflammation, it activates the coagulation pathway via a marked increase in monocyte-associated tissue factor (TF) procoagulant activity, and it inhibits fibrinolysis by promoting the release of PAI-1, contributing to undegraded fibrin deposition. Therefore, we were interested in evaluating, in patients with venous leg ulcers, the effect of pentoxifylline administered at 1,200 mg daily (versus placebo) for 2-months, as this drug induces a decrease in TNF-alpha synthesis and also blocks its activity. This pilot assay was performed in blind. Evolution of several parameters in ulcer biopsies are analyzed: TNF-alpha, intact fibrin, fibrin degradation products, ICAM-1, TF, and elastase. Pentoxifylline administration induced a decrease of local elastase and of fibrin deposit. These results support the hypothesis that accumulation of activated leukocytes is the key event in venous leg ulcers.

Evidence from in vivo manipulations of lipid composition in mutants that the delta 3-trans-hexadecenoic acid-containing phosphatidylglycerol is involved in the biogenesis of the light-harvesting chlorophyll a/b-protein complex of Chlamydomonas reinhardtii

The phosphatidylglycerol containing the unusual delta 3-trans hexadecenoic fatty acid is specifically found in photosynthetic membranes of eukaryotic organisms. Its involvement in the biogenesis and the structure of the light-harvesting chlorophyll a/b-protein complex has been evidenced by in vivo targeting this lipid to photosynthetic membranes of Chlamydomonas reinhardtii mutants lacking this lipid. In the mf1 and mf2 mutants, this deficiency results in (a) the absence of the oligomeric light-harvesting complex of photosystem 2; (b) an extensive destacking of thylakoid membranes; (c) a very low 77-K fluorescence emission in the photosystem-2 region. We show in this paper that these deficiencies result from modifications in the pigment and polypeptide compositions of the photosystem-2 light-harvesting complex; it contains less chlorophyll b and some of its constitutive polypeptides are absent or reduced in amount, while immunologically related polypeptides of lower molecular mass accumulate. The direct involvement of the lack of trans-C16: 1-phosphatidylglycerol in these deficiencies is evidenced by the partial restoration of normal characteristics of the light-harvesting complex (pigment and polypeptide composition, oligomerization) after liposome-mediated, in vivo incorporation of this lipid into the photosynthetic membranes of the mf2 mutant. Trans-C16:1-phosphatidylglycerol, therefore, is involved in the biogenesis of the photosystem-2 light-harvesting chlorophyll a/b-protein complex through a mechanism that may prevent degradation processes. Its contribution to the structural conformation of neosynthesized monomers and to their organization into stable oligomeric form is discussed.

Properties of the mineralocorticoid receptor immunopurified from bovine kidney

The mineralocorticoid receptor (MCR) from bovine kidney was purified on an affinity column containing covalently linked polyclonal IgG raised in the rabbit against rat kidney protein purified in the presence of RU 26752 that is specific to the MCR. The immuno-affinity eluate was excluded as a single peak during gel permeation chromatography and could be resolved as a single band of approximately 98 kDa by western blot and gel electrophoresis. Immunohistochemistry revealed MCR-specific staining in both the cortical and glomerular regions of bovine kidney. Interestingly, the purified MCR could not be activated in the presence of the specific ligand RU 26752 whereas binding to DNA-cellulose increased by 100% when crude cytosol was left at room temperature for 45 min. The binding of calcium to the MCR resulted in an increase in the fluorescence signal that could be partially reversed by EDTA. By a calcium-specific fluorescence dye technique, 1.13 nM of ionized Ca2+ was bound per 0.01 nM MCR. The binding of ATP32 to the immunopurified receptor was observed following chromatography on P-10 columns. The fluorescence signal of etheno-ATP was maximally attenuated by the receptor at 1/1 stoichiometry of the ATP-MCR complex. Asparagine-linked complex chain N-glycosylation of the purified MCR was also observed. Analysis by far-UV circular dichroism spectra showed that MCR contains 33% alpha helices and 30% beta sheets, compatible with a relatively flat conformation of the native protein. These data provide experimental proof for the predicted computer simulation regarding the structural features of the steroid receptor superfamily and suggest crosstalk between several protein families.

Recombinant hirudin: a specific thrombin inhibiting anticoagulant for hemodialysis

The first experience with hirudin as an alternative anticoagulant for heparin in hemodialysis is reported. Recombinant hirudin (HBW 023) was administered in 20 patients as a bolus before dialysis with low flux polysulfone dialyzers (PS400), the dosage being adapted stepwise from patient to patient by 0.02 mg/kg to the occurrence of clotting or bleeding. Four different administration schedules were studied. The first three schedules (0.02 mg/kg, N = 1; 0.04 mg/kg, N = 1; 0.06 mg/kg, N = 4) were discontinued because of clotting. The 0.08 mg/kg schedule was maintained without clotting event in 14 patients. Bleeding was not observed. Plasma hirudin averaged 503.9 +/- 214.0 and 527.7 +/- 217.1 ng/ml after two and four hours of dialysis, and decreased during an interdialytic interval of 44 hours to 223.2 +/- 86.2 ng/ml. Modified antithrombin III (P < 0.05) and activated partial thromboplastin times were lower (P < 0.01) under hirudin compared to heparin; these coagulation parameters were closer to normal during hirudin treatment. The patients developing clotting could be distinguished from those without clotting by the registration of the activated clotting times (9.2 +/- 3.0 vs. 18.7 +/- 3.2 min after 2 hr, P < 0.01; 8.1 +/- 3.0 vs. 16.2 +/- 3.8 min after 4 hr of dialysis, P < 0.05); cut-off value below which clotting is to be expected was 12 min). It is concluded that administration of hirudin as a bolus before the start of dialysis, at a dosage of 0.08 mg/kg, is not complicated by clotting or by bleeding. Coagulation tendency can optimally be monitored by the registration of the activated clotting time.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicotiana tabacum contains a putative mineralocorticoid receptor

Total protein from N. tabacum cell cytosol, partially purified by ammonium sulphate precipitation, contains a 52 kDa protein that tests positive for mineralocorticoid receptor (MCR)-like activity by Western blots, immuneprecipitation and photochemical cross-linking. Binding of RU 26752, a ligand specific to the MCR, suggests 100 fmol steroid bound per mg of tobacco protein; this is equivalent to about 6000 sites per cell assuming a 1/1 stoichiometry. Northern blots of total RNA from isolated tobacco cells, hybridized with a probe specific to mammalian MCR, revealed 2.8 kb and 2.2 kb transcripts, whereas the poly A mRNA was resolved as a prominent message of 1500 bp, preceded by a band of 2200 bp. This appears to be the first ever demonstration where a vascular plant is endowed with a pygmy protein similar to the much larger steroid hormone receptors in the animal world.

Light-induced changes in S-antigen (arrestin) localization in retinal photoreceptors: differences between rods and cones and defective process in RCS rat retinal dystrophy

The subcellular localization of S-antigen (arrestin), a protein regulating phototransduction in retinal rods, was studied by immunocytochemistry using monoclonal antibodies on sections of Swiss mouse, Lewis, Brown Norway (BN), Royal College of Surgeons (RCS) rdy-p+ (dystrophic) and RCS rdy(+)-p (non-dystrophic) rat retinas. In normal retinas, the topography of S-antigen immunoreactivity in photoreceptor cells varied according to the lighting environment of the animals. In dark-adapted eyes, outer segments did not display any S-antigen immunoreactivity while the inner segments, cell bodies and synaptic terminals were strongly labeled. A few minutes after light exposure, there was an inversion of the pattern of labeling: the label increased in the outer segment but was strongly reduced in the other compartments. After 1 h of light, S-antigen immunoreactivity remained only in outer segments and in a few synaptic terminals. We show that the kinetics of this change is slower in cone than in rod cells, and thus allows the transient visualization of the scarce cone photoreceptors. On the 17th day after birth, photoreceptor cells are well differentiated in all rat strains, including RCS rdy-p+ rats. At this time, the S-antigen shift phenomenon occurred in the non-dystrophic strains, but was not observed in rdy-p+ rats: after light exposure, the intracellular distribution of S-antigen remained the same as in the dark. We suggest that an abnormality in the mechanisms of intracellular protein transport could be a characteristic of this genetic disease.

Immunochemical detection of the mineralocorticoid receptor in rat brain

The mineralocorticoid receptor (MCR) in the brain of adult male rats was analyzed with the aid of an antiserum generated by immunizing rabbits with this protein purified biochemically from rat kidney. In Western blots, the antibody recognized a single band of protein of about 98 kD from all target tissues studied to date. The granular cells in the cerebellum appeared to be the richest region of the central nervous system in the MCR analyzed by dot blots and by immunoperoxidase staining. High immunoreactivity was also observed in the dorsal and ventral hippocampus, as well as the anterior, mediobasal and posterior hypothalamus. In contrast, midbrain, septum and striatum were MCR-negative. The antibody macroaggregated and precipitated brain MCR labelled with 3H-aldosterone but did not recognize 3H-RU 26752 bound nonspecifically to non-MCR proteins in whole brain cytosol. Thus, MCR function and expression in the adult rat brain need to be reassessed.

Dusart syndrome: a new concept of the relationship between fibrin clot architecture and fibrin clot degradability: hypofibrinolysis related to an abnormal clot structure

Fibrinogen Dusart is a congenital dysfibrinogenemia (A-alpha 554 Arginine-->Cysteine) associated with severe thrombotic disorder, high incidence of thrombotic embolism, and abnormal fibrin polymerization. This thrombotic disorder was attributed to an abnormal clot thrombolysis with reduced plasminogen binding to fibrin and defective plasminogen activation by tissue plasminogen activator. The purpose of this work was to assess whether clot architecture could be involved in the thromboresistance of the fibrin Dusart and the high incidence of embolism. An important change in Dusart fibrin clot structure was identified with dramatic decrease of gel porosity (Ks), fiber diameters (d), and fiber mass-length ratios (mu) derived from permeation analysis. In addition, rigidity of the Dusart clot was found to be greatly increased compared with normal fibrin. We provide evidence that both thrombolysis resistance and abnormal rigidity of the fibrin Dusart are related to this abnormal architecture, which impairs the access of fibrinolytic enzymes to the fibrin and which is responsible for a brittle clot that breaks easily, resulting in a high incidence of embolism. Indeed, when restoring a normal clot structure by adding dextran 40 (30 mg/mL) before coagulation, clot thrombolysis and clot rigidity recovered normal values. This effect was found to be dose-dependent. We conclude that clot architecture is crucial for the propensity of blood clot to be degraded and that abnormal clot structure can be highly thrombogenic in vivo. The alpha-C domains of fibrinogen are determinant in fibrin clot structure.

Potent activity of peripheral blood lymphocytes in inducing hepatocyte stimulating factor and urokinase in monocytes

As fibrinogen is an independent risk factor for arterial thrombosis we were interested in analysing the mechanism controlling fibrinogen biosynthesis. In this work, we showed that incubation of monocytes with lymphocytes increased hepatocyte stimulating factor (HSF) production. Different mechanisms are involved and our results demonstrated that this effect is in part mediated by an increase in interleukin 6 (IL-6) production. However, IL-6 cannot account for the whole effect and other cytokines could be implicated. In addition, we observed a stimulation of urokinase-type plasminogen activator (u-PA) associated with monocytes when these cells were incubated with lymphocytes for 18 h at 37 degrees C. By producing fragment D (fibrinogen degradation product) and D-dimer (fibrin degradation product) this fibrinolytic activity might also contribute to fibrinogen biosynthesis by hepatocytes.

Incubation of monocytes with adriamycin increases secretion of hepatocyte stimulating factor for fibrinogen biosynthesis

This work provides evidence that the production by monocytes of hepatocyte stimulating factor(s) for fibrinogen biosynthesis was dramatically increased when monocytes were exposed to Adriamycin. This effect was related to an increased production of leukaemia inhibiting factor (LIF), a cytokine known to stimulate fibrinogen biosynthesis by hepatic cells. Adriamycin also induces an increase in membrane-associated urokinase on monocytes. These results are consistent with the clinical observation in patients with ovarian cancer that when the CA-125 tumour marker decreases during chemotherapy, an increased level of D-dimer is a marker of good prognosis.

Receptor mediated mineralocorticoid action in alga cell mutants

The multiplication of Chlamydomonas cells can be arrested by the spirolactone derivative RU 26752 and this is fully reversible by the natural hormone aldosterone. Continuous growth in the presence of RU 26752 led to the isolation of a population subsequently resistant to the action of mineralocortoid analogues, due possibly to the selection of mutant cells. Immunophotochemical evidence is provided for a 52 kDa protein that possesses functional steroid and DNA binding domains. Alga cells therefore appear to respond to steroid hormones in a manner similar to the mammalian systems, possibly via a receptor that may represent a pygmy ancestor of the latter day steroid receptor superfamily.

Mineralocorticoid hormone action in plant cells

The multiplication of Chlamydomonas reinhardtii wild type cells can be arrested by the spirolactone RU 26752 and this is fully reversible by the natural mineralocorticoid aldosterone. Evidence is presented for a 52 kDa protein that possesses functional DNA and ligand binding domains and tests positive for mineralocorticoid receptor-like activity by immuneprecipitation, macroaggregation, and photoaffinity. The regulation of trans-activation by steroid hormones in the animal world would therefore appear to be just as valid for the plant kingdom, thereby providing a new model for genetic analysis.

D-dimer and CA 125 levels in patients with ovarian cancer during antineoplastic therapy. Prognostic significance for the success of anti-cancer treatment

In patients with ovarian cancer before they receive chemotherapy, the level of fibrin degradation products (D-dimer), is correlated with the tumor load. In this study, the evolution of D-dimer was compared in patients receiving antineoplastic therapy with the evolution of the disease. The patients could be classified into three groups. In Group 1 (nine patients), both plasma CA 125 (a tumor-associated antigen) and D-dimer remained elevated; the prognosis was always poor. In Group 2 (eight patients), CA 125 and D-dimer decreased simultaneously, complete remission was observed in two patients, and significant residual tumor was observed in the others. In Group 3 (nine patients), despite an important decrease in CA 125, D-dimer remained elevated during therapy. In this group, complete remission was observed in six patients, and three others showed a large decrease in their tumor load. The combination of a decrease in CA 125 levels with a continuous enhanced level of D-dimer during chemotherapy identified a subgroup of patients with a favorable prognosis.

Immunological characterization of an immunomodulatory epitope in S-antigen/arrestin with a sequence motif common to tumor necrosis factor alpha

Some monoclonal antibodies (mAbs) to retinal S-antigen recognize a phylogenetically conserved epitope (S2) in the N-terminal part of the protein. These antibodies have been shown to inhibit the induction of experimental autoimmune uveoretinitis by S-antigen in rats. Using Pepscan method, we localized this epitope on the amino acid (aa) residues 40-50, i.e., PVDGVVLVDPE (peptide S2). MAb binding was confirmed by ELISA, competition-ELISA and dot blot. Other S-antigen peptides with homologies to epitope S2 and peptides exhibiting the pathogenic and T-cell proliferation inducing sites did not bind these mAbs. Epitope S2 displays an immunological crossreactivity with human tumor necrosis factor (TNF) alpha. Recent results indicate that both peptide S2 and a peptide from human TNF alpha (aa residues 31-53) containing the common sequence motif GVxLxD induce TNF alpha production in monocytes. We analyzed the fine structure of the common epitope by studying mAb binding in an amino acid residue exchange experiment.

Inhibition of S-antigen-induced experimental autoimmune uveoretinitis by active immunization against anti-idiotypic antibody to an S-antigen epitope

Experimental autoimmune uveoretinitis (EAU) was induced in rnu/+ rats by one injection of retinal S-antigen (S-Ag) in complete Freund's adjuvant. Immunization of rats, before the S-Ag challenge, with a polyclonal antibody directed at the monoclonal antibody (mAb) S2D2, prevented the development of EAU in rats at clinical and histological levels. Lymph node cells from rats hyperimmunized with this anti-idiotype (anti-Id) S2D2 antibody were stimulated in vitro by anti-Id S2D2, S-Ag, and mAb S2D2. These findings suggest that anti-S2D2 antibody acts as an internal image at the T-cell level for the epitope of S-Ag recognized by mAb S2D2 (epitope S2). From these results, it appears that cells bearing receptors for the internal image of the epitope S2, which is not pathogenic when injected emulsified in adjuvants, are able to inhibit S-Ag-induced EAU.

Immunophotochemical analysis of mineralocortin by polyclonal antibodies against the native receptor from rat kidney

We have obtained a polyclonal antiserum by immunizing fawn Burgundy rabbits with the mineralocorticoid receptor (MCR) purified biochemically from rat kidneys. High titers of anti-MCR activity were obtained in radioimmunoassays within 3 weeks and increased with a booster shot. In Western blot analysis, the antibody revealed a major band of 94-98 kDa in renal cytosol from rat and beef kidneys. We also developed a fluorographic procedure where the MCR linked covalently to tritiated R-5020, following ultraviolet irradiation, gave imprints superimposable on the Western blot profile. The fluorographic pattern was specific since it was largely abolished in the presence of cold RU 26752 that is specific to MCR, or mineralocortin. The immune IgG precipitated rat renal MCR(-)[3H]RU 26752 complexes in a dose-dependent manner and also recognized MCR bound to the natural hormone aldosterone. During gel permeation chromatography on Sephacryl, the elution profile of [3H]RU 26752 shifted to high-molecular-weight regions in the presence of immune IgG. The receptor protein could be immunolocalized primarily to the principal cells of the collecting duct in rat kidney but the intercalated cells and glomeruli were not labeled, contrary to beef kidney where a uniform pattern of immunostaining was evident. These should permit large-scale purification of the MCR for detailed physicochemical studies and for screening of the MCR-positive tissues during various pathophysiological syndromes.

Generation of polyclonal antibodies against the mineralocorticoid receptor and analysis of mineralocortin in rat myocardium by immunophotochemistry

Fawn, Burgundy rabbits were immunized with the mineralocorticoid receptor (MCR) purified biochemically from rat kidney by a simple, two step procedure. High anti-MCR titers were observed in radioimmunoassays just 3 weeks after the initial injection and increased further with time. Western blot analysis revealed a single band of 94-98 kDa in renal and cardiac cytosol from the rat, like the antigen prepared biochemically. The two atria from beef heart exhibited far greater MCR-positivity compared to the two ventricles, suggesting physiological relevance. The receptor was also photolabelled for the first time with promegestone in this very 94-98 kDa region which could be displaced by the antagonist RU 26752 specific to MCR. The immune IgG precipitated 3H-aldosterone or 3H-RU 26752-MCR complexes from rat heart, and displaced the MCR-antagonist complex to high molecular weight regions during gel permeation chromatography on Sephacryl columns. Immunofluorescent labelling showed that MCR was widely distributed in the cytoplasm in rat myocardium with limited staining in what appeared to be the nuclear compartment. These open up the possibility of large scale purification of the endogenous mineralocorticoid binding protein, mineralocortin, for detailed physicochemical characterization. The technique of photoaffinity labelling presented here should also help delineate the nature of the steroid binding domain in the MCR.

Rat lung possesses the mineralocorticoid receptor

Lung cytosol from male, adrenalectomized rats was screened for the mineralocorticoid receptor (MCR) by a polyclonal antiserum raised in the rabbit against rat renal antigen. Western blot analysis revealed a single 98 kDa band, like the MCR purified biochemically. The MCR could also be photolabelled for the first time by 3H-R 5020 in this very 98 kDa region that was displaced by RU 26752 specific to MCR. Immune IgG was able to precipitate the MCR-3H-RU 26752 complex, and to displace the same to high molecular weight regions during gel permeation chromatography on Sephacryl columns. Thus, MCR mediated actions need to be redefined. Furthermore, the technique of photochemical labelling forms a novel tool to assess MCR specificity, and to dissect its structure and function.

A common epitope on human tumor necrosis factor alpha and the autoantigen ‘S-antigen/arrestin’ induces TNF-α production

A common epitope on S-antigen (arrestin), a potent autoantigen inducing experimental autoimmune uveoretinitis (EAU), and on human tumor necrosis factor alpha (hTNF alpha) was revealed using two monoclonal antibodies to S-antigen which inhibit EAU induction. The minimal common sequence for monoclonal antibody recognition is GVxLxD in the S-antigen/hTNF alpha amino acid sequences. Peptides containing this sequence motif exhibited monocyte activating capacity similar to the autocrine stimulatory capacity of hTNF alpha itself. In the S-antigen this activity was located from residue 40 to 50, corresponding to the peptide PVDGVVLVDPE (epitope S2). In hTNF alpha, the monocyte activating capacity correlated to residue 31 to 53, corresponding to the peptide RRANALLANGVELRDNQLVVPSE (peptide RRAN). The identified regions define common functional structures in the autoantigen and in the hTNF alpha molecule. The data suggest a regulatory function of this particular structure in TNF alpha expression and in autoimmunity.

Effect of heparin and enoxaparin on platelet interaction with fibrin clots

It has been recently shown that platelet-rich thrombi are particularly resistant to thrombolysis. Since unfractionated heparin was reported to enhance fibrinogen binding to platelets responsible for the hyperaggregating effect of this drug, the purpose of this work was to determine whether or not heparin could also modulate platelet interaction to whole blood clot. We have therefore investigated the retention to a standard clot of 111In-labelled platelets suspended in plasma in presence of saline (control), heparin or a low molecular weight heparin (Enoxaparin). We have shown that the platelet interaction to the clot was significantly increased by heparin but not by enoxaparin used at the same anti Xa activity. In conclusion, this difference may favor the use of enoxaparin over heparin in clinical situation associated with platelet retention to fibrin clot, such as thrombolysis.

Immunodetection and localization of protein(s) related to retinal S-antigen (arrestin) in kidney

S-antigen (arrestin) is a cytosolic protein which regulates phototransduction in retinal rods. A protein immunologically related to S-antigen was identified in fractions from soluble extract of bovine kidney enriched by gel filtration or by immunoaffinity chromatography using a polyclonal antibody to retinal S-antigen. On immunoblots, this protein was recognized by a panel of monoclonal antibodies (mAbs S2D2, S1A3 and S9E2) directed against different S-antigen epitopes and displayed the same apparent molecular mass (48 kDa) as retinal S-antigen. All three mAbs revealed a specific immunoreactivity by indirect immunocytochemical technique on rat kidney sections. The three mAbs recognized some but not all glomerular cells, identified as epithelial cells by immunoelectron microscopy using the mAb S9E2. Both mAbs S2D2 and S1A3 gave a diffuse cytoplasmic staining in all tubule cells. Proximal tubule cells exhibited a weak immunoreactivity, whereas distal and collecting tubule cells were strongly labeled. In contrast, the mAb S9E2 immunoreaction was restricted to a cell subpopulation from distal and collecting tubules corresponding to intercalated cells identified by immunoelectron microscopy. With the mAb S9E2, the labeling of proximal tubule cells was localized in the apical region of the cytoplasm. These results suggest that two or more 48-kDa proteins immunologically cross-reactive with retinal S-antigen are present in kidney. The observed pattern of distribution is in keeping with the hypothesis that such proteins could play a role in the regulation of G-protein-related receptors present in renal glomerulus and tubule epithelial cells.

Humoral immune response against the S-antigen/TNF alpha common epitope in rat EAU suppressed by the monoclonal antibody S2D2

S-antigen (S-Ag)-induced experimental autoimmune uveoretinitis (EAU) in rats can be suppressed by injecting the mouse monoclonal antibody (mAb) S2D2 or a polyclonal rat anti-idiotype S2D2 (anti-Id S2D2) antibody, the internal image of the epitope of S-Ag recognized by mAb S2D2. This epitope located in amino acids 40-50 of bovine S-Ag (peptide S2), displays an homology with a sequence of human tumor necrosis factor alpha (hTNF alpha) (peptide RRAN) which is also recognized by S2D2. (Stiemer et al., this symposium). We show that one injection of S2D2 at the time of immunization with S-Ag suppressed EAU and modulated the production of antibodies against peptides of bovine or human S-Ag containing the S2 epitope and against peptide RRAN. Immunization against anti-Id S2D2 stimulated antibody production to peptide S2 and RRAN and inhibited EAU. These data suggest that disease suppression could be related to the production of antibodies against the S-Ag/TNF alpha common epitope.