Positive immunoselection using antibody-enzyme complexes

Immunohistochemical localization of catalase in ocular tissue

Localization of catalase in rat and bovine ocular tissues was investigated by an immunohistochemical method. Antisera to purified catalase was raised in a rabbit. Purity of catalase was determined by gel electrophoresis and specificity of the antibody was tested by immunoblot. The immunohistochemical method revealed the presence of catalase predominantly in epithelial and endothelial structures of the eye and in the retina, except in the outer segments. Catalase was found in abundance in those structures that are frequently exposed to oxygen metabolites under physiologic conditions and in such pathologic states as intraocular inflammations. These findings thus suggest that catalase, along with other antioxidant enzymes, may offer protection against the damaging effects of hydrogen peroxide.

Protection of cultured endothelial cells from hydrogen peroxide-induced injury by antibody-conjugated catalase

The cytoprotective features of catalase-antibody conjugate prepared by covalent conjugation of catalase to rabbit antibody against mouse IgG is described. The bifunctional cross-linking agent m-maleimidobenzoic acid N-hydroxysuccinimide ester (MBS) was used for conjugation. Functionally active conjugate binds specifically to the plastic-adsorbed mouse IgG and to the surface of live human endothelial cells treated with mouse antiserum against human endothelial cells. Up to 4 units of catalase activity can bind to 1 cm2 of the endothelial monolayer. The targeted catalase protects endothelial cells from cytotoxic action of hydrogen peroxide: the minimal cytotoxic concentration of H2O2 for protected cells is 80-times higher than for intact cells. This effect is attributed partly to local reduction of H2O2 concentration in the cell microenvironment. Targeted catalase was estimated to reduce H2O2 concentration 8-fold near the cell surface with respect to average total concentration.

Isolation of highly malignant Thy-1-positive revertants from cultured cloned Thy-1-negative lymphoma cells of low tumorigenicity

We have used a positive immunoselection method to isolate a Thy-1-positive revertant of a Thy-1-negative line. The technique makes use of the ability of surface bound antigen-antibody complexes containing the enzyme catalase to protect cells from the toxic effects of hydrogen peroxide. The revertant cells produce a Thy-1 molecule indistinguishable from that produced by the original parent line, and they resemble that line in being far more tumorigenic than the Thy-1-negative variant.

Cell separation: a review

This review summarizes currently available techniques for cell separation. Techniques that exploit differences in physical properties of cells are widely used but have a number of limitations. Those that are based on differences in surface properties may more readily permit reproducible separation of a functionally homogeneous population of cells. Unfortunately very few techniques achieve separation of cells on the basis of differences in their functional characteristics.

Cell separation using positive immunoselective techniques

Positive immunoselection is the direct selection and recovery of cells which express a given specificity from among a heterogeneous group of contaminating cells. A variety of methods are available to effect such separations. The principles of affinity chromatography, using solid-phase matrices or cellular immunoadsorbents, are extensively used. Liquid-phase positive immunoselection can also be performed using either a fluorescence-activated cell sorter or by using 'cellular engineering' to protect a cell from an otherwise noxious environment. The enzyme catalase coupled to specific antibody has been used for this purpose and renders cells resistant to hydrogen peroxide. The various positive immunoselection techniques available are reviewed and evaluated in the following report.