The effects of nonionic polymers on human red blood cell (RBC) aggregation were investigated. The hydrodynamic radius (Rh) of individual samples of dextran, polyvinylpyrrolidone, and polyoxyethylene over a range of molecular weights (1,500-2,000,000) were calculated from their intrinsic viscosities using the Einstein viscosity relation and directly measured by quasi-elastic light scattering, and the effect of each polymer sample on RBC aggregation was studied by nephelometry and low-shear viscometry. For all three polymers, despite their different structures, samples with Rh <4 nm were found to inhibit aggregation, whereas those with Rh >4 nm enhanced aggregation. Inhibition increased with Rh and was maximal at approximately 3 nm; above 4 nm the pro-aggregant effect increased with Rh. For comparison, the Rh of 12 plasma proteins were calculated from literature values of intrinsic viscosity or diffusion coefficient. Each protein known to promote RBC aggregation had Rh >4 nm, whereas those with Rh <4 nm either inhibited or had no effect on aggregation. These results suggest that the influence of a nonionic polymer or plasma protein on RBC aggregation is simply a consequence of its size in an aqueous environment, and that the specific type of macromolecule is of minor importance.

BACKGROUND. Rapid clearance of poly(ethylene glycol)‐asparaginase (PEG‐ASNase) has been reported for up to one‐third of patients treated for acute lymphoblastic leukemia (ALL), potentially rendering their treatment ineffective. A 25% occurrence of an antibody against PEG (anti‐PEG) was previously reported in healthy blood donors. The objective of the study was to determine whether anti‐PEG was associated with rapid clearance PEG‐ASNase. METHODS. The investigation reanalyzed stored sera from pediatric patients enrolled in the ALL Berlin‐Frankfurt‐Muenster 2000 studies. Twenty‐eight samples were selected to include 15 subjects with undetectable ASNase activity after receiving PEG‐ASNase. Sixteen subjects treated with unmodified ASNase were also included, 8 with low ASNase activity. Sera were tested for anti‐PEG using 2 techniques: 1) serology, by agglutination of PEG‐coated red blood cells; 2) flow cytometry, by analysis of 10 μm PEG beads stained for bound immunoglobulins. RESULTS. Of the 15 sera from PEG‐ASNase‐treated patients with undetectable ASNase activity, anti‐PEG was detected in 9 by serology and in 12 by flow cytometry. Anti‐PEG was detected in 1 PEG‐ASNase‐treated patient with lower ASNase activity (123 U/L). No relation was observed between anti‐PEG and serum ASNase activity for patients treated with unmodified ASNase. CONCLUSIONS. The presence of anti‐PEG was very closely associated with rapid clearance of PEG‐ASNase. Further comprehensive studies are warranted to fully elucidate the effect of anti‐PEG on PEG‐conjugated agents. Screening and monitoring for anti‐PEG may allow identification of patients for whom a modified dosing strategy or use of a non‐PEGylated drug would be appropriate. Cancer 2007. © 2007 American Cancer Society.

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Traditional formulations of bone wax are composed largely of beeswax and are well known to interfere with bone healing and cause inflammatory reactions. Ostene, a newly available bone hemostasis agent made of water-soluble alkylene oxide copolymers, was evaluated. The soft tissue response to Ostene was compared with bone wax and a polyethylene control after implantation into the paravertebral muscles of three rabbits. After 2 weeks, Ostene elicited no fibrous response, the polyethylene elicited a thin (less than 0.5 mm) fibrous response, and the bone wax was encased in a fibrous capsule 0.6 to 1.0 mm thick infiltrated with inflammatory cells. The effects of Ostene were compared with bone wax in a femur defect model in eight rabbits. Ostene showed no evidence of an adverse response in the cortical defect site, medullary cavity, or the surrounding tissue at 4 and 8 weeks. In contrast, bone wax at both time intervals elicited a foreign body response consisting of fibrous tissue infiltrated by macrophages, giant cells, and lymphocytes at the sites of the bone defects. Bone wax also displaced the bone marrow and interfered with bone ingrowth into the defects. Ostene provides the clinician a water-soluble bone hemostasis material that does not demonstrate the adverse tissue response or the interference with bone healing seen with the use of bone wax.

These results indicate the importance of plasma-mediated RBC interactions and suggest that the benefits of transfusion may vary depending on local flow rates (i.e., shear rates) and organ-specific hemodynamics.

It has been proposed that abnormal mechanical properties may contribute to capillary retention of polymorphonuclear leukocytes (PMN) in sepsis, leading to the development of organ dysfunction. The present study was designed to determine whether PMN rigidity is increased in severe sepsis, and whether changes in the rheologic behavior of PMN correlate with the clinical course in sepsis. Eighteen adults with severe sepsis were studied over a period of 14 d; 11 survived and seven died. PMN deformation behavior was investigated via micropore filtration, using the cell transit analyzer. On Day 0, PMN rigidity was 2.5-fold greater for sepsis patients than for five normal controls (p < 0.001). PMN rigidity progressively improved over the 14 d study period for patients who recovered, but not for those who died; clinical indicators correlated with PMN rigidity. Patient PMN also exhibited a 5-fold greater increase in rigidity in response to formyl-methionylleucylphenylalanine (fMLP) than did control PMN. Both the increased rigidity and enhanced response to fMLP could be simulated in vitro by incubation of normal PMN with tumor necrosis factor-alpha (TNF-alpha). We conclude that circulating PMN are more rigid in severe sepsis, and are "primed" for an augmented response to chemotactic stimuli. These findings support the hypothesis that cytokine-mediated increases of PMN rigidity may lead to sequestration of these cells in capillaries and to the consequent impairment of microvascular perfusion in sepsis.

Hemoglobinopathies, such as β-thalassemias and sickle cell anemia (SCA), are among the most common inherited gene defects. Novel models of human erythropoiesis that result in terminally differentiated red blood cells (RBCs) would be able to address the pathophysiological abnormalities in erythrocytes in congenital RBC disorders and to test the potential of reversing these problems by gene therapy. We have developed an in vitro model of production of human RBCs from normal CD34+ hematopoietic progenitor cells, using recombinant growth factors to promote terminal RBC differentiation. Enucleated RBCs were then isolated to a pure population by flow cytometry in sufficient numbers for physiological studies. Morphologically, the RBCs derived in vitro ranged from early polylobulated forms, resembling normal reticulocytes to smooth biconcave discocytes. The hemoglobin pattern in the in vitro-derived RBCs mimicked the in vivo adult or postnatal pattern of β-globin production, with negligible γ-globin synthesis. To test the gene therapy potential using this model, CD34+ cells were genetically marked with a retroviral vector carrying a cell-surface reporter. Gene transfer into CD34+ cells followed by erythroid differentiation resulted in expression of the marker gene on the surface of the enucleated RBC progeny. This model of human erythropoiesis will allow studies on pathophysiology of congenital RBC disorders and test effective therapeutic strategies.