Severe bleeding can occur in patients with vancomycin-induced immune thrombocytopenia. The detection of vancomycin-dependent antiplatelet antibodies in patients receiving the antibiotic in whom thrombocytopenia develops, and the absence of antibodies in patients given the drug in whom platelet counts remain stable, indicate that these antibodies are the cause of the thrombocytopenia.

Higher ADPN and lower WHRs (higher peripheral adiposity) are associated with better metabolic health in both nonobese and obese white individuals. These results suggest that ADPN and peripheral adiposity play a key role in determining the metabolic health independent of body mass index.

Drug-induced immune thrombocytopenia (DITP) is a serious and sometimes life-threatening complication of treatment with many drugs. In most instances (excluding heparin-induced TP), platelet (plt) destruction is caused by antibodies (abs) that recognize distinct epitopes on platelet membrane glycoproteins (GP) only when the sensitizing drug is present in soluble form. How drug at pharmacological levels promotes tight binding of antibody to a specific target is unknown, in part because only polyclonal human abs have been available for study. We sought to produce monoclonal abs (mAbs) that mimic the behavior of human drug-dependent abs to create tools that can be used to study the molecular basis for this interaction. Mice were immunized with GPIIb/IIIa isolated from human platelets together with soluble quinine (Qn), tirofiban (Tf), or eptifibatide (Ef), three drugs that commonly cause DITP. Hybridomas were prepared from splenic B cells using a standard protocol and approximately 550 supernatants from each cultured hybrid line were screened for DDAbs by flow cytometry using normal platelets as targets. To date, 11 Abs that react with GPIIb/IIIa only in the presence of the immunizing drug (2 Qn-, 3 Tf- and 6 Ef-specific) have been identified. Preliminary studies show that the Qn-specific abs bind reversibly to GPIIb/IIIa at 50 nM Qn, a concentration much lower than is achieved pharmacologically, and are not inhibited by Qn at 5 mM, the limit of solubility. Quinidine (Qd) the diastereoisomer of Qn, supports only weak ab binding at a concentration of 50 uM. The tirofiban and eptifibatide-dependent abs recognize GPIIb/IIIa occupied by these RGD ligand-mimetic GPIIb/IIIa inhibitors. In each of these respects, reaction patterns of the three groups of mAbs closely resemble those of abs from patients experiencing TP after treatment with one of these drugs. These findings show that mAbs mimicking the behavior of human drug-dependent abs can be produced by immunizing mice with GP and soluble drug to produce probes suitable for characterizing the molecular basis of ab-drug-target interactions leading to platelet destruction in DITP. It is noteworthy that these mAbs were induced using soluble drug and protein for immunization because this suggests that the immune response leading to DITP does not require the sensitizing drug to be covalently linked to a protein, i.e, does not require the drug to act as a classical hapten.

Numerous drugs are known to cause immune thrombocytopenia (TP) mediated by antibodies (abs) that bind to platelets only when the sensitizing drug is present in soluble form. The widely used antibiotic, vancomycin, has been implicated as a cause of TP only in 8 case reports and little is known about antibodies possibly responsible for this complication. We characterized clinical and serologic aspects of TP occurring in 39 patients during treatment with vancomycin. In this group, TP developed after 1–27 days of treatment (median 6 days) and plt nadirs ranged from 1,000 to 60,000 plts/uL (median 14,000 plts/uL). Bleeding occurred in 14 patients and contributed to a fatal outcome in 3. TP persisted for 1–17 days after discontinuing vancomycin (median 7 days). Platelets eventually returned to baseline in all surviving patients. Serum obtained after the onset of TP was studied for vancomycin-dependent, platelet-reactive abs by flow cytometry and by solid phase ELISA using immobilized plt glycoproteins (GP) as targets. Vancomycin-dependent antibodies detected in patients and normal subjects IgG only IgM only IgG + IgM No antibody Total Patients with TP 21 (54%) 5 (13%) 13 (33%) (0)%) 39 Normal individuals 58 (21%) 4 (1%) 1 (0%) 210 (77%) 273 Results of flow cytometric studies are summarized above. All patients had IgG and/or IgM abs that reacted with normal plts in the presence, but not in the absence of vancomycin. The IgG mean fluorescence intensity (MFI) signal in the presence of drug was 1.6 to 32.0 times stronger (mean ratio 5.7) than that obtained in the absence of drug. Vancomycin-dependent IgG abs were also identified in 59 of 273 normal individuals but were much weaker than abs detected in patients (p = 0.004). IgM abs (mean ratio 5.7, range 1.6 – 34) were found in 18 of 39 patients (46%). Weaker IgM abs were found in only 5 of 273 normal subjects (1.8%) (p = 0.001). Two patient abs studied in ELISA reacted preferentially with GPIIb/IIIa. Studies to determine the frequency of abs in patients given vancomycin who do not develop TP are in progress. These findings provide evidence that TP in patients given vancomycin can be caused by drug-dependent abs specific for GPIIb/IIIa that are stimulated by vancomycin exposure. IgG and IgM abs in patients with TP are generally much stronger than drug-dependent, platelet-reactive immunoglobulins found in some normal subjects. The significance of the latter abs is presently unknown. Drug-dependent IgM abs are found almost exclusively in patients with vancomycin-associated TP and may be diagnostic. Patients treated with vancomycin often have life-threatening bacterial sepsis and may have various reasons for developing TP. Serologic testing for drug-dependent, platelet-reactive IgG and IgM abs may provide a means of identifying those in whom vancomycin should be discontinued.