Extracorporeal removal of circulating immune complexes: from non-selective to patient-specific

Device for continuous extracorporeal blood purification using target-specific metal nanomagnets

BACKGROUND

The present work illustrates how magnetic separation-based blood purification using ultra-strong iron nanomagnets can be implemented into an extracorporeal blood purification circuit. By this promising technique, today's blood purification may be extended to specifically filter high-molecular compounds without being limited by filter cut-offs or column surface saturation.

METHODS

Blood spiked with digoxin (small molecule drug) and interleukin-1β (inflammatory protein) was circulated ex vivo through a device composed of approved blood transfusion lines. Target-specific nanomagnets were continuously injected and subsequently recovered with the aid of a magnetic separator before recirculating the blood.

RESULTS

Magnetic blood purification was successfully carried out under flow conditions: already in single-pass experiments, removal efficiencies reached values of 75 and 40% for digoxin and interleukin-1β, respectively. Circulating 0.5 L of digoxin-intoxicated blood in a closed loop, digoxin concentration was decreased from initially toxic to therapeutic concentrations within 30 min and purification extents of 90% were achieved after 1.5 h.

CONCLUSIONS

Magnetic separation can be successfully implemented into an extracorporeal blood purification device. Simultaneous and specific filtering of high-molecular compounds may offer promising new therapeutic tools for the future treatment of complex diseases, such as sepsis and autoimmune disorders.

Polyclonal Antibody-Induced Serum Sickness in Renal Transplant Recipients: Treatment with Therapeutic Plasma Exchange

Serum sickness is an immune-complex mediated illness that frequently occurs in patients after polyclonal antibody therapy (ATGAM or thymoglobulin). Serum sickness presents with significant morbidity but is self-limited and resolves with prolonged steroid therapy. We present five renal transplant patients who developed serum sickness after polyclonal antibody treatment with severe symptoms that persisted after being started on systemic steroids. These patients underwent one or two courses of therapeutic plasma exchange (TPE) with subsequent complete resolution of their symptoms. Renal transplant recipients with serum sickness after polyclonal antibody therapy may benefit from TPE by accelerating their time to recovery and thereby reducing overall morbidity.

The current status of therapeutic apheresis devices in the United States

Over the last 40 years, plasmapheresis technology and its indications for use have been continually evolving. With the growing incidence for autoimmune diseases, unsatisfactory therapeutic options, side effects of drug therapy, and economic relevance, apheresis clinicians have been leaning toward more selective plasmapheresis techniques through the use of plasma fractionators and immunoadsorption columns. Plasma fractionators are mostly used in Asia, and rarely utilized in the U.S. The majority of plasma filters approved by the Food and Drug Administration (FDA) are primary membrane plasma separators, which still require replacement fluid. The secondary plasma fractionators available in the U.S. are limited in used and mostly investigational. Immunoadsorption columns, mostly used in Europe, are gaining popularity in the U.S. Some FDA-approved immunoadsorption columns include the Prosorba protein-A silica column, Immunosorba tryptophan and phenylalanine columns, Immunosorba protein-A sepharose column, and Liposorber dextran sulfate column. In addition, the heparin-induce extracorporeal lipoprotein precipitation (HELP) system is also FDA-approved. However, there are other immunoadsorption technologies used in Europe, such as direct adsorption lipoprotein LDL-hemoperfusion, not yet available in the U.S. While each method of apheresis carries its own risks and benefits, it is the opinion of the authors that these additional apheresis techniques be available to U.S. researchers and clinicians as a therapeutic option. The authors believe that the U.S. need to aggressively investigate more specific plasmapheresis modalities and establish appropriate dialogue with regulatory and reimbursement officials for FDA-approval of these devices.

Background and indications for protein A-based extracorporeal immunoadsorption

Protein A (SPA), a major cell wall component of Staphylococcus aureus, has occupied numerous investigators from its discovery in the late fifties. Its availability and avid binding to human immunoglobulins have led to extensive usage for diagnostic and research purposes. Today, SPA-based extracorporeal immunoadsorption relies on two rather different systems, namely, SPA-silica (Prosorba), and SPA-Sepharose (Immunosorba). Both systems are approved by the Food and Drug Administration for the core indications of rheumatoid arthritis and idiopathic thrombocytopenic purpura (SPA-silica) or hemophilia with inhibitors (SPA-Sepharose). Off label indications include immune disorders with a conceivable connection between autoantibody titers and disease activity, like forms of glomerulonephritis, systemic lupus erythematodes, myasthenia, and the Guillain-Barré syndrome as well as alloantibody formation in the context of e.g., transplantation. This review summarizes historical developments and important properties of SPA. Indications for extracorporeal therapy are discussed on the basis of available information and personal experience.

Membrane, intracellular, and plasma magnesium and calcium concentrations in preeclampsia

Changes in intracellular calcium and magnesium concentrations seem to be involved in the pathogenesis of preeclampsia, whereas the role of cell membranes has not been studied in detail yet. To investigate the changes in calcium and magnesium metabolism in normal pregnancy and preeclampsia, plasma, intracellular, and membrane calcium and magnesium concentrations were determined in a clinical study. Twenty-five control, 18 untreated healthy pregnant, and 16 nulliparas preeclamptic women were investigated. Plasma, cellular, and membrane (erythrocytes) calcium and magnesium contents were measured by atomic absorption spectroscopy. Plasma and intracellular magnesium concentrations were significantly lower in the healthy pregnant group and the preeclamptic group as compared to controls (P < .01). In erythrocyte membranes magnesium content was found significantly decreased in the preeclamptic women as compared to healthy subjects (P < .001). There was a significant decrease in the plasma calcium concentration in the preeclamptic group compared to controls or healthy pregnant women (P < .05). Membranous calcium content was significantly increased in the preeclamptic group versus controls or healthy pregnant women (P < .001) and an inverse correlation with membranous magnesium content was found (r = -0.79,P < .01). Lowered plasma, intracellular, and membrane magnesium concentrations in preeclampsia may contribute to the development in hypertension in pregnancy. In addition, a disturbed calcium homeostasis is observed in preeclampsia.