ristocetin and Multiple-Myeloma

Acquired von Willebrand syndrome (AvWS) is an uncommon complication of multiple myeloma (MM), and it is believed to be connected with paraprotein. The aim of this study was to determine the incidence of AvWS in patients with MM, and estimate the role of paraprotein in its occurrence. The study included 40 patients with MM. The plasma level of paraprotein, platelet adhesion on glass pearls, plasma von Willebrand factor antigen concentration, and ristocetin-induced platelet aggregation (RIPA) were measured initially. Absence of RIPA was found in six patients with MM (15%); however, all six of them had normal levels of von Willebrand factor antigen. Paraprotein was isolated from the serum of these patients. Platelet aggregation was measured in six healthy donors before and after addition of the isolated paraprotein. RIPA was significantly decreased in healthy donors in the presence of paraprotein (P<0·001). The same test was repeated with added human immunoglobulins for intravenous use without any change in RIPA. A significant negative correlation between plasma paraprotein level and RIPA was found (P<0·001). These investigations have shown that paraprotein is associated with AvWS in patients with MM.

Topics: Adult; Aged; Aged, 80 and over; Blood Coagulation Tests; Female; Humans; Male; Middle Aged; Multiple Myeloma; Paraproteins; Platelet Aggregation; Ristocetin; von Willebrand Diseases

A 49-year-old man with multiple myeloma (IgG-lambda Bence-Jones protein positive) presented a bleeding tendency: characterized intramuscular hemorrhage. Coagulation studies showed a von Willebrand factor (vWF) defect (Duke bleeding time > 20 min; ristocetin cofactor activity [vWF:RC] < 6%; significant reduction of large multimers of vWF. Mixing study suggested the presence of inhibitor directed against vWF:RC activity and collagen binding activity of vWF. The inhibitor was identified as an antibody of the IgG class. The inhibitor blocked the interaction of vWF with glycoprotein Ib in the presence of ristocetin, as did the pepsin-digested fragment of the inhibitor [F(ab)2'], but neither blocked botrocetin-mediated interaction of vWF with glycoprotein Ib. They also inhibited the binding of vWF to immobilized collagen type I. The inhibitor and the F(ab)2' reacted strongly with native vWF and fragment I (amino acids 911-1365) and with the 39/34 kDa fragment (amino acids 480/481-718), but not with fragment II (amino acids 1366-2050) and fragment III-T2 (heavy chains, amino acids 273-511; light chains, amino acids 674-728). We conclude that the IgG antibody inhibits both vWF:RC activity and the binding of vWF to collagen by reacting with the epitopes present on the A1 loop and A3 domains of vWF.

Topics: Autoantibodies; Binding Sites, Antibody; Binding, Competitive; Collagen; Humans; Immunoglobulin G; Male; Middle Aged; Multiple Myeloma; Platelet Glycoprotein GPIb-IX Complex; Protein Binding; Protein Structure, Tertiary; Ristocetin; von Willebrand Factor

Acquired von Willebrand disease (vWD) has been described in a few patients with multiple myeloma. The present study characterizes an inhibitor of von Willebrand factor (vWF) isolated from a patient with multiple myeloma (IgG-kappa). Multimeric analysis of vWF from this patient's plasma showed a reduction in multimers of all sizes. The inhibitor (IgG) detected only the vWF subunit from plasma of normal individuals. It reacted with intact vWF subunit and a 39/34kDa dispase-digested fragment of vWF (residues; Leu480/Val481-Gly718), but did not react with platelet membrane glycoproteins (GPs) or adhesive proteins. The binding of vWF to GPIb mediated by ristocetin and by botrocetin was inhibited by the patient's IgG with an IC50s of 0.3 mg/ml and 0.48 mg/ml, respectively. The platelet aggregation induced by ristocetin or botrocetin was also inhibited by the IgG. These results indicate that this inhibitor may recognize the binding region of vWF to GPIb. Therefore, the antibody to vWF appears to represent the likely pathophysiological mechanism responsible for the acquired vWD in this patient.

Topics: Autoantibodies; Binding Sites; Blotting, Western; Crotalid Venoms; Humans; Immunoglobulin G; Macromolecular Substances; Male; Middle Aged; Multiple Myeloma; Platelet Aggregation; Platelet Membrane Glycoproteins; Ristocetin; von Willebrand Diseases; von Willebrand Factor

Topics: Animals; Antibodies, Monoclonal; Blood Platelets; Cell Separation; Chromatography, Affinity; Chromatography, Gel; Humans; Indicators and Reagents; Mice; Mice, Inbred BALB C; Multiple Myeloma; Platelet Membrane Glycoproteins; Ristocetin; Spleen

In a case of severe IgG kappa myeloma with cryoglobulinaemia usual concentrations of epinephrine, collagen, ADP, arachidonic acid, thrombin and ristocetin caused no aggregation of platelets in platelet rich plasma. However, in contrast to other agents ristocetin induced platelet aggregation in higher concentrations. The investigations showed, that the aggregating activity was inhibited by binding of ristocetin to the abnormal protein. Following saturation of the monoclonal protein, the surplus ristocetin caused normal aggregation. This indicates that platelets actually preserved their responsiveness to ristocetin. Possible causes of the phenomenon are discussed.

Topics: Aged; Cryoglobulinemia; Female; Hemorrhagic Disorders; Humans; Immunoglobulin G; Immunoglobulin kappa-Chains; Multiple Myeloma; Platelet Aggregation; Protein Binding; Ristocetin; von Willebrand Diseases