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Biomedical subjects

S Dzik

Publications and source records attributed to S Dzik.

16 recordsLinked to original sources
PubMed2000

A multicenter study evaluating three methods for counting residual WBCs in WBC-reduced blood components: Nageotte hemocytometry, flow cytometry, and microfluorometry.

BACKGROUND: A multicenter study was conducted to evaluate the performance characteristics of flow cytometry and microfluorimetry for counting low concentrations of WBCs and to compare the results with Nageotte hemocytometry. STUDY DESIGN AND METHODS: A two-phase study involving 10 centers located in the United States and in Europe was performed. Coded samples of RBCs and platelets were distributed by 24-hour (Phase 1) or 2-day (Phase 2) courier service to each test site for analysis. Samples were prepared to include concentrations of WBCs slightly above and below the concentration corresponding to the threshold standards for WBC-reduced RBCs and platelets. All centers tested samples by Nageotte hemocytometry plus one or both of two automated methods. RESULTS: Both flow cytometry and microfluorometry gave better results than Nageotte hemocytometry in testing freshly prepared samples. At WBC concentrations >5 per microL (RBCs) or >3 per microL (platelets), the intersite CV was <20 percent for the automated methods but >30 percent for the Nageotte hemocytometer method (p<0.001). Accuracy was greater for the automated methods than for the Nageotte hemocytometer method (p<0. 001). Nageotte hemocytometry showed a bias to underestimation relative to the results obtained with the automated methods. All methods had poorer performance in testing samples that required > or =2 days' shipment than in testing of those requiring overnight shipment. CONCLUSION: Automated methods for counting residual donor WBCs in WBC-reduced cellular components offer advantages of improved precision and greater accuracy than are seen with the Nageotte hemocytometer method. Automated methods are less labor-intensive but more costly than microscopic methods. Preparation and shipping methods will need further refinement for samples to be counted more than 24 hours after sample collection.

Blood Platelets↗
PubMed1996

Current research on the immunomodulatory effect of allogeneic blood transfusion.

This review summarizes three aspects of current research on the immunomodulatory effect of allogeneic transfusion. Representatives of three laboratories-each of which is actively engaged in research on transfusion-induced immunomodulation-summarize their current investigative approach. First, current animal models of transfusion-induced immunomodulation are presented and research on the tumor growth-promoting effect of allogeneic transfusion is described. Second, mechanisms underlying an immunomodulatory effect of transfusion are summarized and experiments on the induction of transplant tolerance by selective introduction of donor-type MHC antigens is presented. Third, the potential clinical impact of increased infection and tumor recurrence resulting from transfusion-induced immunomodulation is assessed. The potential role of donor-derived hematopoietic stem cells is presented as an area of future investigation in the area of transfusion-induced immunomodulation.

Adoptive Transfer↗
PubMed1994

Prestorage leukocyte reduction of cellular blood components.

With the increasing demand for leukoreduced cellular blood components, many blood centers in Europe, North America, and Asia have begun to prepare leukocyte depleted cellular blood components prior to storage. Increased understanding of transfusion complications resulting from recipient exposure to residual donor leukocytes has focused attention on donor leukocytes during blood storage. This review examines production options for prestorage leukocyte removal, considers approaches to quality control, discusses proposed laboratory and clinical advantages of leukoreduction prior to storage compared with after storage, and suggests a strategy for cost-effective implementation of widespread prestorage leukocyte removal.

Blood Banks↗
PubMed1994

HLA antigens on leukocyte fragments and plasma proteins: prestorage leukoreduction by filtration.

HLA alloimmunization following blood transfusion results from recipient exposure to donor alloantigens. Numerous studies have documented that intact donor leukocytes are capable of provoking primary alloimmunization and that leukoreduction can decrease the incidence of primary HLA alloimmunization. HLA antigens also exist in soluble form and are present on leukocyte cell fragments. We measured the concentration of soluble HLA class I antigen in both standard and leukoreduced blood components during storage. Although the concentration of soluble class I HLA protein varied widely among different individuals, the concentration was stable during refrigerated storage of red cell concentrates and was not affected by leukocyte reduction by filtration. We also investigated whether or not HLA antigens present on leukocyte fragments were capable of stimulating either resting or in-vitro-primed lymphocytes in the mixed lymphocyte reaction (MLR).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Preservation↗
PubMed1993

Leukodepletion blood filters: filter design and mechanisms of leukocyte removal.

Modern leukocyte removal filters have been developed after years of refinement in design. Current filters are composite filters in which synthetic microfiber material is prepared as a nonwoven web. The filter material may be surface modified to alter surface tension or charge to improve performance. The housing design promotes effective contact of blood with the filter material and decreases shear forces. The exact mechanisms by which these filters remove leukocytes from blood components are uncertain, but likely represent a combination of both physical and biological processes whose contributions to leukocyte removal are interdependent. Small-pore microfiber webs result in barrier phenomena that permit retention of individual cells and increase the total adsorptive area of the filter. Modifications in surface charge can increase or decrease cell attraction to the fibers. Optimum interfacial surface tensions between blood cells, plasma, and filter fibers not only permit effective blood flow through small fiber pores, but also facilitate cell contact with the material. Barrier retention is a common mechanism for all modern leukocyte-removal filters and applies to all leukocyte subtypes. Because barrier retention does not depend on cell viability, it is operative for cells of any age and will retain any nondeformable cell, including whole nuclei from lymphocytes or monocytes. Barrier retention is supplemented by retention by adhesion. RBCs, lymphocytes, monocytes, granulocytes, and platelets differ in their relative adhesiveness to filter fibers. Different adhesive mechanisms are used in filters designed for RBCs compared with filters designed for platelets. Although lymphocytes, monocytes, and granulocytes can adhere directly to filter fibers, the biological mechanisms underlying cell adhesion may differ for these cell types. These differences may depend on expression of cell adhesion molecules. In the case of filtration of fresh RBCs, platelet-leukocyte interaction seems to supplement other mechanisms of leukocyte retention. The interactions of cells with biomaterials is an area of important research for implantable medical devices, artificial organs, and orthopedic, vascular, and dental prosthetics. Research in these areas is likely to contribute to improved biomaterials for blood filters. Improved techniques for the preparation of hybrid polymers and new techniques for surface modification of existing polymers will increase the technical opportunities for the development of synthetic surfaces ideally designed for leukocyte removal. It is therefore likely that the performance of leukocyte-removal filters will continue to improve. The development of cost-effective leukocyte removal filters specifically designed for use during component preparation would permit leukocyte depletion of all cellular blood components.

Biomechanical Phenomena↗