An in vitro system for testing leucocyte and leukaemic cell line adhesion to synthetic fibres

Endothelial Cell Participation in Inflammatory Reaction

Inflammation is an old concept that has started to be considered as an important factor in infection and chronic diseases. The role of leukocytes, the plasmatic components, then of the mediators such as prostaglandins, cytokines, and, in recent decades, of the endothelium has completed the concept of the inflammation process. The function of the endothelium appeared to be crucial as a regulator or the initiator of the inflammatory process. Culture of human endothelial cells and experimental systems made it possible to define the molecular basis of inflammation in vascular diseases, in diabetes mellitus, atherosclerosis, vasculitis and thromboembolic complications. Advanced glycation end product receptor (RAGE), present on endothelial cells (ECs) and monocytes, participates in the activation of these cells in inflammatory conditions. Inflammasome is a cytosolic multiprotein that controls the response to diverse microorganisms. It is positively regulated by stimulator of interferon response CGAMP interactor-1 (STING1). Angiogenesis and thrombotic events are dysregulated during inflammation. ECs appear to be a protector, but also a possible initiator of thrombosis.

Cellular and Molecular Aspects of Blood Cell-Endothelium Interactions in Vascular Disorders

In physiology and pathophysiology the molecules involved in blood cell–blood cell and blood cell–endothelium interactions have been identified. Platelet aggregation and adhesion to the walls belonging to vessels involve glycoproteins (GP), GP llb and GP llla and the GP Ib–IX–V complex. Red blood cells (RBCs) in normal situations have little interaction with the endothelium. Abnormal adhesion of RBCs was first observed in sickle cell anemia involving vascular cell adhesion molecule (VCAM)-1, α4β1, Lu/BCAM, and intercellular adhesion molecule (ICAM)-4. More recently RBC adhesion was found to be increased in retinal-vein occlusion (RVO) and in polycythemia vera (PV). The molecules which participate in this process are phosphatidylserine and annexin V in RVO, and phosphorylated Lu/BCAM and α5 laminin chain in PV. The additional adhesion in diabetes mellitus occurs due to the glycated RBC band 3 and the advanced glycation end-product receptors. The multiligand receptor binds advanced glycation end products (AGEs) or S100 calgranulins, or β-amyloid peptide. This receptor for advanced glycation end products is known as RAGE. The binding to RAGE-activated endothelial cells leads to an inflammatory reaction and a prothrombotic state via NADPH activation and altered gene expression. RAGE blockade is a potential target for drugs preventing the deleterious consequences of RAGE activation.

TCR-mediated functions are enhanced in activated peripheral blood T cells isolated from leucocyte reduction systems

Buffy coats are the most common method for the acquisition of activated primary human T cells for research or clinical applications, but recently leukocyte reduction system (LRS) cones have emerged as a viable source for these cells. In this study, we determined if activated human T cells derived from buffy coats or LRS cones had different functionality. No changes in the expression of surface receptors were observed except for a significant increase in CD44 expression on T cells isolated from LRS cones. LRS cone-derived T cells trended towards higher receptor-mediated cytokine production and had significantly increased donor-to-donor variability in IFN-γ production. TCR-induced ERK1/ERK2 and AKT phosphorylation was also increased in T cells isolated from LRS cones. In conclusion, LRS cones are an excellent source of T cells for clinical and research applications, but these cells have subtle functional differences from T cells isolated using standard buffy coats.

Functionalization of Poly(ethylene terephthalate) Fibers by Photografting of a Carbohydrate Derivatized with a Phenyl Azide Group

Grafting of a new carbohydrate UV-reactive molecule, an azidophenyl lactamine (AzPhLac), was achieved on fibers of three different diameters: 12, 18, and 32 microm. Adsorption of AzPhLac on fibers was obtained by using the dip-coating method in solution. The effect of the solution concentration on surface density and yield of grafted AzPhLac was investigated. Surface densities in the range 3-67 nmol/cm2 were obtained without marked difference related to the diameter of the fiber. Quantitative grafting was obtained with a surface of fiber of 1 cm2 and the lowest concentration (0.5 mM) of AzPhLac solution. The surface density and grafting yield decreased with the available surface of the fibers. This phenomenon could be attributed to a masking core-shell effect with outer fibers in the shell preventing the UV grafting of the fibers located in the core of the fibers' bundles. Scanning electron (SEM) and atomic force (AFM) microscopic observations suggested that homogeneous grafting might be obtained.

Whole-blood leukoreduction filters are a source for cryopreserved cells for phenotypic and functional investigations on peripheral blood lymphocytes

BACKGROUND

Leukoreduction of blood is now widely performed by blood banks, and the possibility of recovering 10(8) to 10(9) white blood cells (WBCs) from leukoreduction filters, which are usually discarded, represents a promising source for normal human cells. Previous studies with these filters to prepare WBCs have performed their experimentation with fresh cells only. Whether these filter-derived cells could also be used to prepare frozen cell banks to facilitate work organization and open new avenues for their utilization as references in physiological studies and clinical investigations was investigated.

STUDY DESIGN AND METHODS

Blood samples or whole-blood leukoreduction filters were obtained, after informed consent, from volunteers or blood donors, respectively. The proportions of CD3+, CD14+, CD16+, CD19+, and CD45+ cells within peripheral blood mononuclear cells (PBMNCs) were determined by flow cytometry from all samples. B cells were isolated and their functional responses were evaluated in vitro.

RESULTS

The yield of PBMNCs recovered from whole-blood leukoreduction filters was lower (50%) than the one with fresh blood samples but still provided 2 x 10(8) to 4 x 10(8) PBMNCs per unit. After one cycle of freezing-thawing, the proportions of B- and T-cell populations were similar to normal blood values. Purified B cells issued from whole-blood leukoreduction filters displayed normal phenotypes and functions.

CONCLUSION

Leukoreduction filters represent a valuable source of PBMNCs. These cells could be easily recovered to prepare frozen cell banks useful in basic phenotypic and functional analyses involving the main subsets of B cells and the global T-cell population.

Filter Buffy Coats (FBC): a source of peripheral blood leukocytes recovered from leukocyte depletion filters

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34(+) hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34(+) cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4(+), CD8(+), CD3(+)), B lymphocytes (CD19(+)), NK cells (CD56(+)), HSC/HPC (CD34(+), CD133(+)) or dendritic cells (BDCA-4(+)). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

Analysis of leukocyte binding to depletion filters: role of passive binding, interaction with platelets, and plasma components

Since limited knowledge exists on the mechanisms which regulate cell binding to leukocyte removal filter surfaces, we investigated the binding patterns of leukocytes to individual layers of leukocyte depletion filters. After passage of 1 unit of whole blood, blotting of isolated filter layers on glass slides or elution of cells from filter layers revealed that most leukocytes were located within the first 10 of a total of 28 filter layers, peaking at layers 6 to 8, with granulocytes binding on average to earlier filter layers than lymphocytes. Leukocytes preincubated with inhibitors of actin activation showed unchanged distribution between filter layers, suggesting that cytoskeletal activation does not significantly contribute to their binding. When leukocytes were directly incubated with single filter layers, binding of up to 30% of input cells was recorded in the absence of Ca(2+). Immunohistological analyses showed colocalization of platelets and leukocytes, with co-clustering of platelets and leukocytes. Monocytes and to some degree lymphocytes but not granulocytes competed with platelets for filter binding. Precoating of filter layers with individual plasma components showed that hyaluronic acid, plasma type fibronectin, and fibrinogen all increased the binding of leukocytes compared with albumin coating. In conclusion, leukocytes can bind passively to filters in a process which does not require Ca(2+), which is independent of cytoskeletal activation and which may depend on individual plasma components. These results are of importance when new selective cell enrichment or depletion strategies through specific filters are envisaged.

CD11b/CD18-dependent interactions of neutrophils with intestinal epithelium are mediated by fucosylated proteoglycans

CD11b/CD18-mediated adhesive interactions play a key role in regulating polymorphonuclear leukocytes (PMN)) migration across intestinal epithelium. However, the identity of epithelial ligands for migrating PMN remains obscure. In this study we investigated the role of carbohydrates in mediating adhesive interactions between T84 intestinal epithelial cells and CD11b/CD18 purified from PMN. Fucoidin, heparin/heparin sulfate, N-acetyl-D-glucosamine, mannose-6-phosphate, and laminarin were found to inhibit adhesion of T84 cells to CD11b/CD18. The most potent inhibitory effects were observed with fucoidin (50% inhibition at 1-5 x 10(-8) M). Binding assays demonstrated that fucoidin directly bound to CD11b/CD18 in a divalent cation- and sulfation-dependent fashion that was blocked by anti-CD11b mAbs. Experiments employing CD11b/CD18 as a probe to blot T84 cell fucosylated proteins purified via fucose-specific lectin column revealed several candidate CD11b/CD18 binding proteins with molecular masses of 95, 50, 30, 25, and 20 kDa. Fucosidase treatment of T84 cells resulted in significantly reduced cell adhesion to CD11b/CD18, while no inhibition was observed after neuraminidase treatment. Finally, significant inhibition of T84 cell adhesion to CD11b/CD18 was observed after blocking cell proteoglycan synthesis with p-nitrophenyl-beta-D-xylopyranoside. These findings implicate epithelial cell surface proteoglycans decorated with sulfated fucose moieties as ligands for CD11b/CD18 during PMN migration across mucosal surfaces.