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A method is described where superparamagnetic polymer microspheres coated with monoclonal antibodies (MoAb) are used for the direct and fast quantification of the absolute number of cells of various lymphocyte subsets in blood. Blood samples were incubated with microspheres coated with a subset specific MoAb, Using a magnet the microsphere-rosetted cells were isolated and washed. Following lysis of the cell walls to detach the microspheres, the cell nuclei were stained with acridine orange and counted in a haemocytometer using an immunofluorescence microscope. With MoAb specific for CD2, CD4, CD8 and CD19, reproducible absolute counts of the corresponding lymphocyte subsets were obtained which correlated closely with those obtained by an indirect quantification method. [ABSTRACT FROM AUTHOR]

The interaction between polymer particles with an immune ligand on their surfaces and normal (hepatocytes) and malignant (Raji) cells with a corresponding membrane receptor was investigated by scanning and transmission electron microscopy. The influence of lime, temperature, and anti-metabolites on this process was studied, the results indicate that when panicles with an immunoligand are added lo cells with a corresponding membrane receptor, three successive Mops are initiated, the first two of which are not dependent on the temperature or the metabolic state of the cells. The first step in this process is the binding of particles to the cell surface through the immunoligand on the particle and the receptor on the cell surface. The initial binding formed by immunoligand and corresponding receptor is followed by a stronger interaction between cell and panicle. This second step seems to be governed by a successive antibody-antigen interaction: the zipper mechanism. A third step in the particle-to-cell interaction is characterized by movements of the cellular surface, as revealed by membrane folds, pseudopods, and lamellae extending from the surface and enveloping large parts of the particle. [ABSTRACT FROM AUTHOR]

We have investigated the possibility to employing magnetic monodisperse polymer particles for positive selection of human peripheral blood mononuclear cell populations. By carefully titrating the ratio between particles and cells we succeeded in isolating a number of cell populations that could be cultivated subsequently in vitro for functional studios. The success of the procedure is partly dependent on the properties of the monoclonal antibodies used to sensitize the cells. Provided these antibodies do not react with membrane structures involved in the transduction of activating signals, highly purified, quiescent cell populations can be recovered in a single fractionation step. In most instances particles will detach from the isolated cells by overnight culture, and the particles can then be removed from the system by a suitable magnet. T lymphocytes, subpopulations of T lymphocytes and B lymphocytes have been isolated in this way and studied in a variety of functional assay systems. Comparison with cells obtained after negative selection clearly demonstates the usefulness of this technique. especially it the membrane marker selected for it is not directly engaged in the activation processes. [ABSTRACT FROM AUTHOR]

Magnetic monodisperse polymer particles were developed and the necessary conditions established to use them for both quantification and fractionation of human peripheral blood mononuclear cell population. The particles consists of a styrene divinylbenzene core into which magnetite has been deposited by an in situ oxidation process. Thereafter the core has been coated with a hydrophilic polymer containing epoxy and hydroxyl groups. The particles have strong nonspecific binding capacity for protein and can be coated with the appropriate antibodies by physical adsorption only. However, the hydroxyl groups on the outer polymer also make covalent coupling possible. After appropriate blocking they can be used in a rosette assay for quantification of mononuclear leukocytes previously sensitized with monoclonal antibodies. Furthermore, a suitable magnet makes it possible to deplete the cell suspension efficiently of the rosette-forming cells. We have thoroughly investigated the functional properties of human mononuclear cells depleted of T lymphocytes by this technique. Our results show that T cells are virtually completely eliminated, as demonstrated by flow cytometry and various functional assay systems. [ABSTRACT FROM AUTHOR]

Macrophages obtained from animals treated with β-1,3-D-glucan-derivatized plastic beads were greatly stimulated, as judged by morphology, esterase release, and cytostatic effect on L-929 tumour cells in vitro. The pretreatment of mice with such beads conferred an apparent absolute local resistance to an otherwise lethal pneumococcal infection but had no effect on the growth of intraperitoneal AA ascites sarcoma. Moreover, peritoneal cells from animals pretreated with glucan beads did not protect the animals in a Winn assay. [ABSTRACT FROM AUTHOR]