No abstract

Tissue rejection occurs subsequent to the recognition of foreign antigens via receptor-ligand contacts between APC (antigen presenting cells) and T cells, resulting in initialization of signaling cascades and T cell proliferation. Bioengineering of donor cells by the covalent attachment of methoxypolyethylene glycol (mPEG) to membrane proteins (PEGylation) provides a novel means to attenuate these interactions consequent to mPEG-induced charge and steric camouflage. While previous studies demonstrated that polymer-mediated immunocamouflage decreased immune recognition both in vitro and in vivo, these studies monitored late events in immune recognition and activation such as T cell proliferation. Consequently little information has been provided concerning the early cellular events governing this response. Therefore, the effect of PEGylation was assessed by examining initial cell-cell interactions, changes to activation pathways, and apoptosis to understand the role that each may play in the decreased proliferative response observed in modified cells during the course of a mixed lymphocyte reaction (MLR). The mPEG-modified T cells resulted in significant immunocamouflage of lymphocyte surface proteins and decreased interactions with APC. Furthermore, mPEG-MLR exhibited decreased NFκB pathway activation, while exhibiting no significant differences in degree of cell death compared to the control MLR. These results suggest that PEGylation may prevent the direct recognition of foreign alloantigens by decreasing the stability and duration of initial cell-cell interactions.

Microfluidic analysis of blood has potential clinical value for determining normal and abnormal erythrocyte deformability. To determine if a microfluidic device could reliably measure intra-and inter-personal variations of normal and oxidized human red blood cell (RBC), venous blood samples were collected from repeat donors over time. RBC deformability was defined by the cortical tension (pN/mm), as determined from the threshold pressure required to deform RBC through 2-2.5 lm funnel-shaped constrictions. Oxidized RBC were prepared by treatment with phenazine methosulphate (PMS; 50 mM). Analysis of the control and oxidized RBC demonstrated that the microfluidic device could clearly differentiate between normal and mildly oxidized (20.13 6 1.47 versus 27.51 6 3.64 pN/mm) RBC. In vivo murine studies further established that the PMS-mediated loss of deformability correlated with premature clearance. Deformability variation within an individual over three independent samplings (over 21 days) demonstrated minimal changes in the mean pN/mm. Moreover, inter-individual variation in mean control RBC deformability was similarly small (range: 19.37-21.40 pN/mm). In contrast, PMS-oxidized cells demonstrated a greater inter-individual range (range: 25.97-29.90 pN/mm) reflecting the differential oxidant sensitivity of an individual's RBC. Importantly, similar deformability profiles (mean and distribution width; 20.49 6 1.67 pN/mm) were obtained from whole blood via finger prick sampling. These studies demonstrated that a low cost microfluidic device could be used to reproducibly discriminate between normal and oxidized RBC. Advanced microfluidic devices could be of clinical value in analyzing populations for hemoglobinopathies or in evaluating donor RBC products post-storage to assess transfusion suitability. Am. J. Hematol. 88:682-689,

BACKGROUND: Whole blood (WB) is held at room temperature for not more than 24 hours before blood component manufacturing. The ability of several culture collection, skin-derived, and transfusion-related bacteria to survive in WB stored at 22 AE 2 C for 24 hours was investigated in this study. STUDY DESIGN AND METHODS: Twenty-onebacteria of the species Staphylococcus epidermidis, Staphylococcus aureus, Staphylococcus capitis, Streptococcus agalactiae, Serratia liquefaciens, Serratia marcescens, Klebsiella pneumoniae, Escherichia coli, and Yersinia enterocolitica were inoculated into 7-mL aliquots of WB at a concentration of 500 colony-forming units (CFU)/mL. Spiked WB was stored aerobically at 22 AE 2 C, and bacterial viability and growth were monitored at 3, 8, and 24 hours during WB storage. Bacteria that showed decreased viability during WB incubation were further characterized for their sensitivity to plasma factors and neutrophil killing. ABBREVIATIONS: AMP(s) = antimicrobial peptide; BA = blood agar; BC-PC(s) = buffy coat platelet concentrate(s); PC(s) = platelet concentrate(s); PI = pathogen inactivation; TSB = trypticase soy broth; WB = whole blood. From the