Interaction of anti-DNA antibodies with synthetic polyanionic antigens.

Autoantibodies to DNA (anti-DNAab), found primarily in systemic lupus erythematosus (SLE), cross-react with a variety of antigens. The binding of these antibodies to naturally occurring mucopolysaccharides such as heparan and chondroitin sulfates has led to the suggestion that anti-DNAab have specificity for a polyanionic epitope. In this study, to avoid the use of endogenous immunogens to which humans may have become sensitized, we have used the synthetic polyanions, dextran sulfate (DS), polyvinyl sulfate (PVS) and the semi-synthetic antigen, pectic acid (PA) to evaluate this hypothesis using SLE sera (n = 15) and sera from healthy individuals (controls; n = 15, age and sex matched to SLE group). Inhibition of binding with 125I-DNA was optimal at 1 mg/ml for DS and PVS, and resulted in significant inhibition of binding by both SLE and control sera of native DNA (P less than 0.01, each group); no inhibition was observed with PA, nor was a significant inhibition observed with any antigen on binding of SLE or control sera groups to denatured DNA. We conclude that while on quantitative grounds reaction of anti-DNAab with polyanions may not be clinically relevant, it is clear that, unlike polycarboxylates (e.g. PA), polysulfated polymers, whether aliphatic, as in the case of PVS, or glycosidic, such as DS, react with a subpopulation of anti-DNAab in such a manner as to block significantly the ability of these antibodies to bind DNA.

[Hemorrhagic syndrome associated with a factor VIII:C inhibitor in a patient with lymphoma]. / Síndrome hemorrágico asociado a un inhibidor del factor VIII:C en un paciente con linfoma.

Acquired hemophilia (idiopathic or secondary) is an uncommon clinical condition. A 70-year-old male had a severe hemorrhagic disorder, and an IgG inhibitor of the factor VIII:C was detected in plasma. During the acute phase he was treated with packed red blood cells, frozen fresh plasma and polyvalent immunoglobulins. The hemorrhagic features subsided but the circulating anticoagulant persisted. The administration of an activated prothrombin complex permitted to make the diagnosis of the underlying disease, a highly malignant T type lymphoma. During the treatment with corticosteroids and polychemotherapy the inhibitor activity disappeared.

A monoclonal immunoglobulin A (kappa) factor VIII:C inhibitor associated with primary amyloidosis: identification and characterization.

Factor VIII:C inhibitors associated with primary amyloidosis have not been previously reported. A patient with autopsy-proved primary amyloidosis developed renal failure requiring peritoneal dialysis. Purpura and a prolonged partial thromboplastin time (PTT) were first observed 3 years later, after treatment was changed from peritoneal dialysis to hemodialysis. Plasma contained a time-dependent factor VIII:C inhibitor. The inhibitor on isoelectric focusing showed two peaks of activity, one with an isoelectric point (pl) of approximately 4 and the second larger, with a pl of approximately 8. Both were neutralized only by antisera to IgA and kappa light chain. A monoclonal antibody prepared in Balb/c mice against the variable region of the kappa light chain also blocked the inhibitor. The delayed onset of the coagulopathy could be explained by the change from peritoneal to hemodialysis, because in the former, significant amounts of the paraprotein, indicated by an "M-spike," were recovered in the dialysate. N-terminal amino acid sequencing of the first 20 amino acids of the variable region of the kappa light chain from the urinary protein and the splenic amyloid subunit showed identity.

Possible mechanism of immunosuppression by gramicidin S of S antigen-induced experimental autoimmune uveoretinitis.

Gramicidin S (GrS) suppressed the onset of experimental autoimmune uveoretinitis (EAU) induced with S-antigen in rats, and the proliferation of mitogen-stimulated lymphocytes in culture. As an immunosuppressive mechanism of the cyclic peptide antibiotic we first postulated that the drug exerts its effect as an ionophore. Although all ionophore compounds tested suppressed lymphocyte proliferation, no correlation was observed between changes in intracellular concentrations of Na+ and K+ and the degree of immunosuppression. For example, monensin inhibited lymphocyte proliferation without affecting intracellular Na+ and K+ levels. Thus it was likely that the immunosuppressive effects of the ionophore compounds including GrS were due to their ability to modify cell membrane properties rather than their ionophore activity. We then tested the hypothesis that GrS inhibits transport of metabolic intermediates or metabolites (thymidine and methionine) into lymphocytes. The idea was experimentally supported. Further, inhibition of metabolite transport by GrS was found to be reversible. To investigate whether inhibition of metabolite uptake can be a mechanism of immunosuppression of EAU, endogenously stimulated lymphocytes were isolated from S-antigen-immunized rats at different stages of EAU and the effect of GrS on metabolite uptake by the cells was determined. The activity of lymphocytes to transport metabolites was enhanced at pre-EAU stages and the enhanced metabolite uptake was markedly inhibited by GrS. We interpreted the result to support that inhibition of metabolite uptake by GrS is probably a mechanism of immunosuppression in vivo by this drug.

Acquired factor VIIIC deficiency due to circulating factor VIIIC inhibitors.

The management of patients with Factor VIIIC inhibitor is frequently a therapeutic challenge. Treatment is often individualized. We describe 3 patients, nonhaemophilic adults, with bleeding diatheses caused by a circulating inhibitor to Factor VIIIC. One patient had long standing rheumatoid arthritis. The other two did not have any apparent underlying disease, although one of them had an antecedent antecedent phenylbutazone injection for arthralgias. Prednisolone was prescribed for two patients which resulted in rapid clinical improvement and the eventual normalization of Factor VIIIC activity. The role and rationale of immunosuppressive therapy in Factor VIIIC inhibitor is reviewed.

Significant increase of urinary low-sulfated heparan-sulfate-related protein in patients with severe systemic scleroderma.

Radioimmunoassay with an antibody produced against urinary low-sulfated heparan-sulfate-related protein was devised and used to screen the heparan sulfate level in the urine of patients with systemic scleroderma. Patients with diffuse scleroderma, and patients also showing polymyositis/dermatomyositis had elevated values, whereas the value in patients with acrosclerotic scleroderma did not differ from that of the control population. In addition, an increase in this protein was associated with the positivity of anti-Scl-70 antibody. These findings suggest an important role for low-sulfated heparan sulfate in the pathobiology of severe systemic scleroderma.

Analysis of CD3-antibody-mediated inhibition of T-cell activation.

In this study the influence of a non-mitogenic anti-CD3 antibody on accessory cell-dependent antigen and mitogen-induced T-lymphocyte proliferation has been investigated. The antibody was found to completely inhibit PHA, Con A, PWM, and tetanus toxoid stimulation, with no effect on the proliferation induced by the calcium ionophore A23187. VIT3 completely abrogated the production of IL-2 by lectin-stimulated T cells. It had no effect, however, on the IL-2-dependent proliferation of preactivated T-cell blasts. In addition, the antibody was able to elevate free cytoplasmic Ca2+ levels within minutes after the addition to T cells. Detailed time kinetic analyses revealed that the time interval critical for inhibition was significantly dependent on the interaction between T cells and accessory cells. Under standard conditions, in the presence of 10% non-T cells as accessory cells 50% inhibition was still achieved when VIT3 was added to PHA-stimulated T cells as late as 8 hr after the onset of culture. Delayed addition or a decrease in the number of added accessory cells significantly prolonged this time period. Lectin-stimulated T cells can thus obviously be inhibited via CD3 as long as they have not received all signals including those delivered by accessory cells. Although the underlying mechanisms are not clear so far, the observation that VIT3 at the same time triggers an early cytoplasmic Ca2+ response might indicate that it thereby actively interferes with antigen and lectin-initiated activation processes.

Acquired factor VIII:C inhibitor (IgG) and positive direct Coombs' test (IgM) in a patient with lung carcinoma. Clinical course and immunochemical studies.

UNLABELLED: A 73-year-old man with lung squamous-cell carcinoma simultaneously developed a factor VIII:C inhibitor and a transient positive direct Coombs' test. The factor VIII:C inhibitor was characterized as a mixture of IgG1, IgG2, IgG4 with kappa and lambda light chains. The Coombs' test was IgM-specific. TREATMENT: blood transfusions (packed red cells), cyclophosphamide and prednisone. Bleeding subsided without factor VIII-replacement therapy. Before death, in spite of the tumour-mass progression, factor VIII:C was normal.

Development of an inhibitor specific to factor VIII: coagulant activity in a patient with platelet-type von Willebrand's disease.

Platelet-type von Willebrand's disease is a recently described autosomal dominant bleeding disorder characterized by decreased ristocetin cofactor activity, lack of the higher molecular weight von Willebrand Factor (vWF) multimers on SDS agarose gel electrophoresis, increased platelet aggregation with low concentrations of ristocetin, and increased ristocetin-induced binding of normal vWF to patient platelets. In this report the authors describe a 17-month-old male with Platelet-type von Willebrand's disease, inherited from the paternal side of his family, who developed an inhibitor specific to Factor VIII:C. The patient's plasma inhibited normal plasma VIII:C and partially purified VIII:C; it did not appear directed against normal VIIIR:Ag or ristocetin cofactor. This antibody is therefore similar to inhibitors that develop in some transfused hemophilia A patients. Since low VIII:C, VIII:CAg, and VIII:C/VIIIR:Ag ratio were encountered in his mother, it is likely that this patient has inherited hemophilia A in addition to Platelet-type von Willebrand's disease.

[Acquired hemophilia A due to factor VIIIC inhibitor: detection of circulating immune complexes containing factor VIIIC but not factor VIIIR]. / Erworbene Hämophilie A durch Faktor-VIIIC-Hemmkörper: Nachweis zirkulierender Immunkomplexe, die nur Faktor VIIIC, nicht aber Faktor VIIIR enthalten.

In a 79-year-old, otherwise healthy woman who had developed multiple hematomas, laboratory tests revealed a factor VIII inhibitor (8.0 Bethesda units) which caused a decrease in factor VIIIC activity to 1%; factor VIIIR antigen and ristocetin cofactor activity were above normal values. Incubation of patient's plasma with a factor VIIIC sepharose immunoadsorbent partially removed the inhibitor, which was again detected in the IgG-containing eluate. In addition, immune complexes were found in the patient's serum. Whereas incubation of the serum with an immunoadsorbent containing rabbit antihuman factor VIIIR antibodies did not influence the titer of the immune complexes, 43% of which were removed by a rabbit antihuman factor VIIIC immunoadsorbent. This suggests that the factor VIIIC part only may be trapped by the inhibitor, leaving the factor VIIIR part of the molecule unchanged in circulation. This hypothesis is further supported by the fact that the amount of factor VIIIR antigen is likewise not diminished by incubation of patient's plasma with Raji cells.

Antigenic competition: cellular or humoral.

The injection of one antigen into mice inhibited the response to a second when 1 to 10 days separated the two injections. When the same type of inhibition was attempted in gamma-irradiated mice reconstituted with normal spleen cells, the inhibition was greater in mice receiving 50 million spleen cells than in those receiving 10 million. The results are interpreted as favoring a humoral mechanism of inhibition.