Prevalence and biological effects of anti-trophoblast and anti-endothelial cell antibodies in patients with recurrent spontaneous abortions.

PROBLEM: Trophoblasts and endothelial cells represent a potential target for antibodies in women with recurrent spontaneous abortions. These antibodies have been shown to be associated with anti-phospholipid antibodies. Are they also present in women with unexplained pregnancy losses in the absence of anti-phospholipid antibodies? METHOD OF STUDY: The anti-trophoblast antibodies were tested by an immunofluorescence assay on cells purified from pooled first-trimester placentae, whereas the anti-endothelial cell antibodies were measured by enzyme-linked immunoadsorbent assay (ELISA) on cells isolated from the umbilical vein and were cultured to confluence. The cytotoxicity of trophoblasts was evaluated in a homologous system. The expression of adhesion molecules on endothelial cells was quantitated by ELISA using specific monoclonal antibodies, and the expression of tissue factor was quantitated by a chromogenic assay measuring the formation of factor Xa. RESULTS AND CONCLUSIONS: Complement-fixing antibodies to trophoblast represent a better marker to discriminate patients with recurrent spontaneous abortions from controls and are cytotoxic for the target cells. Anti-endothelial antibodies are also present in these patients and exhibit pro-inflammatory and pro-coagulant activities.

Susceptibility of human trophoblast to killing by human complement and the role of the complement regulatory proteins.

The susceptibility of trophoblast to cytolysis by human complement was investigated using cells purified to over 90% from first trimester placentae. Two assay systems were employed to measure the killing of trophoblasts, an antibody-dependent complement-mediated cytolysis and the reactive lysis. The antibody obtained from a patient with Addison's disease reacted specifically with syncytiotrophoblasts and induced a dose-dependent killing of the cells not exceeding 50% even in the presence of excess antibody and complement. The percentage of cells killed by the terminal complement complex in the reactive lysis system was somewhat higher, reaching values of 60%. Immunofluorescence analysis revealed the presence of CD46 and CD59 on all syncytiotrophoblasts, whereas CD55 was only detected on approximately 30% of the cells. Inhibition of CD46 and CD59 resulted in increased susceptibility of syncytiotrophoblasts to complement lysis. The protective function of CD55 could not be evaluated because of its reduced expression on isolated trophoblasts. These results suggest that syncytiotrophoblasts may be killed by complement and that membrane regulators to some extent protect these cells from complement damage.

Monoclonal antibodies as probes to investigate the molecular changes of C5 associated with the different stability of the molecule on sheep erythrocytes and Escherichia coli 0111:B4.

The fifth C component (C5) exhibits a different stability when bound to sheep E or Escherichia coli 0111:B4, being fairly stable on the bacterial intermediate sensitized E. coli 0111:B4 coated with C components up to C5 (BAC1-5) and extremely labile on the RBC intermediate sensitized sheep E coated with C components up to C5 (EAC1-5). We examined the possibility that molecular changes of membrane-bound C5 might be responsible for the different functional behavior of the two intermediates using mAb to C5 and sensitive immunoassays to detect bound C5. The decay of EAC1-5 over 30 min of incubation at 37 degrees C was associated with a significant drop in the reactivity of bound C5 with three of four mAb used. These results contrasted with those obtained with BAC1-5, which showed unchanged reactivity with all mAb tested over the same period of incubation. The effect of mAb on the activity of C5 was then investigated in an attempt to relate the change of the reactivity pattern of EAC1-5 with the functional modification of bound C5. MAb 1.5 and 1.6 were the only antibodies that interfered with the functional activity of C5, although through a different mechanism. In particular, mAb 1.5 was active both on fluid-phase and on membrane-bound C5 and is therefore likely to interact with the binding site for the late components on C5. Conversely, mAb 1.6 was only effective on fluid-phase C5 and acted by promoting a decay of BAC1-5 similar to the spontaneous decay of EAC1-5. We suggest that the bacterial outer membrane may protect C5 from functional decay and that mAb 1.6 interferes with the stabilizing effect of the bacteria in an as yet unclear manner.

Immunological patterns in monoarticular juvenile rheumatoid arthritis.

Seven pediatric patients with monoarticular arthritis, three of whom had a recent onset form and the remaining four a disease of longer duration, were examined for possible modifications of their immunological parameters. The diagnosis of JRA was made on all these patients according to the ARA criteria after a follow-up of at least two years. Humoral and cellular abnormalities of the immune system were searched for in peripheral blood, synovial fluid and synovial membrane. No evidence for complement consumption and for increased levels of immune-complexes was found in the sera and in the synovial fluids of these patients, who were all seronegative. Some patients had antinuclear antibodies in their sera and synovial fluids. With regard to the lymphocyte distribution, whereas only some patients had an increased number of circulating B cells, the majority had a decreased CD4+/CD8+ ratio in the synovial fluid compared to the ratio found in the peripheral blood. A massive infiltration of CD4+ cells and macrophages and the presence of a substantial number of OKT9+ cells was found in the synovial membranes.

Life-threatening reaction to factor VIII concentrate in a patient with severe von Willebrand disease and alloantibodies to von Willebrand factor.

A 16-yr-old girl with severe von Willebrand disease complicated by the development of precipitating alloantibodies to von Willebrand factor (anti-VWF) had a life-threatening anaphylactoid reaction immediately after the infusion of a commercial plasma concentrate of factor VIII/von Willebrand factor. An early post-infusion activation of the complement system was demonstrated by the appearance of C3 split products and by the drop of serum CH50 activity, occurring in parallel with a post-infusion drop in the anti-VWF antibody levels. Immune complexes remained unchanged in the early post-infusion period and rose to a moderate extent only after 24 h. We conclude that biologically active products of the complement system contributed to the onset of this life-threatening reaction which occurred after concentrate infusion.

A computerized microassay for complement hemolytic activity using an automated spectrophotometer.

A microassay carried out with V-bottomed microplates was developed as a simplified procedure to estimate the complement hemolytic activity. This microassay has the advantage of permitting the evaluation of the extent of lysis without the need to separate the supernatants from the unlysed erythrocytes. This is accomplished by calculating the ratio between the absorbance at 405 nm and that at 450 nm. The results, read automatically on a Dynatech MR580 spectrophotometer, are transformed into CH50 U by means of a computer program. Finally, a kinetic assessment of complement hemolytic activity, easily carried out by this simple procedure, may reveal complement abnormalities otherwise undetected by the standard hemolytic assay.