A Robust Method for Assaying the Immunoreactive Fraction in Nonequilibrium Systems.

The immunoreactive fraction r provides important information on the functional purity of radiolabeled proteins. It is traditionally determined by saturating the radioimmunoconjugate with an increasing excess of antigen, followed by linear extrapolation to infinite antigen excess in a double inverse "Lindmo plot". Although several reports have described shortcomings in the Lindmo plot, a systematic examination is lacking. Using an experimental and simulation-based approach, we compared-for accuracy, precision and robustness-the Lindmo plot with the "rectangular hyperbola" extrapolation method based on the Langmuir model. The differences between the theoretical and extrapolated r values demonstrate that nonequilibrium and antigen depletion are important sources of error. The mathematical distortions resulting from the linearization of the data in the Lindmo plot induce fragility towards stochastic errors and make it necessary to exclude low bound fractions. The rectangular hyperbola provides robust and precise r estimates from raw binding data, even for slow kinetics.

Antibody-labeled liposomes for CT imaging of atherosclerotic plaques: in vitro investigation of an anti-ICAM antibody-labeled liposome containing iohexol for molecular imaging of atherosclerotic plaques via computed tomography.

We evaluated the specific binding of anti-intercellular adhesion molecule 1 (ICAM-1) conjugated liposomes (immunoliposomes, or ILs) to activated human coronary artery endothelial cells (HCAEC) with the purpose of designing a computed tomographic imaging agent for early detection of atherosclerotic plaques. Covalent attachment of anti-ICAM-1 monoclonal antibodies to pre-formed liposomes stabilized with polyethylene glycol yielded ILs, with a coupling efficiency of the ICAM-1 to the liposomes of 10% to 24%. The anti-ICAM-1-labeled ILs had an average diameter of 136 nm as determined by dynamic light-scattering and cryogenic electron microscopy. The ILs' encapsulation of 5-[N-acetyl-(2,3-dihydroxypropyl)-amino)-N, N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-benzene-1,3-dicarboxamide (iohexol) was determined to be 18% to 19% by a dialysis technique coupled with ultraviolet detection of free iohexol. This encapsulation corresponded to 30 to 38 mg iodine per mL IL solution, and the ILs exhibited 91% to 98.5% iohexol retention at room temperature and under physiologic conditions. The specific binding of the ILs to cultured, activated HCAEC was measured using flow cytometry, enzyme-linked immunosorbent assays, and fluorescence microscopy. The immunosorbent assays demonstrated the specificity of binding of anti-ICAM-1 to ICAM-1 compared with control studies using nonspecific immunoglobulin G-labeled ILs. Flow cytometry and fluorescence microscopy experiments demonstrated the expression of ICAM-1 on the surface of activated HCAEC. Therefore, our iohexol-filled ILs demonstrated potential for implementation in computed tomographic angiography to noninvasively detect atherosclerotic plaques that are prone to rupture.

Platelet-derived microparticles and the potential of glycoprotein IIb/IIIa antagonists in treating acute coronary syndrome.

Platelet glycoprotein IIb/IIIa receptors are major platelet membrane constituents. They are integral to the formation of the surface fibrinogen receptor on activated platelets, in which 73% of platelet-derived microparticles are positive for the glycoprotein IIa/IIIb receptor. Activated platelets can shed platelet-derived microparticles, especially during the course of an acute coronary syndrome. Data have shown that platelet-derived microparticles can bind to the endothelium, to leukocytes, and to the submatrix of vascular walls, and launch some signal-transduction pathways, such as the pertussis-toxin-sensitive G protein, extracellular signal-regulated kinase, and phosphoinositide 3-kinase pathways. One research group found that platelet-derived microparticles transfer glycoprotein IIb/IIIa receptors to isolated and whole-blood neutrophils. The receptors can co-localize with beta(2)-integrins and cooperate in the activation of nuclear factor kappaB (NF-kappaB), which can be inhibited by glycoprotein IIb/IIIa receptor antagonists. Accordingly, it is possible that glycoprotein IIb/IIIa receptor antagonists produce a direct and marked effect on endothelial cells, smooth-muscle cells, and leukocytes through a platelet-derived microparticle pathway that will lead to a potential treatment for acute coronary syndrome.Herein, we review the medical literature and discuss the potential application of platelet-derived microparticles toward the treatment of acute coronary syndrome.

Procedimientos para la detección e identificación de anticuerpos eritrocitarios / Procedures for the detection and identification of red cell antibodies

En Inmunohematología se ha desarrollado una amplia gama de procederes de detección e identificación de anticuerpos eritrocitarios in vitro, por lo cual se realiza una revisión de técnicas y métodos empleados con este objetivo, como son el método que utiliza eritrocitos pretratados con enzimas proteolíticas y las técnicas de Polibreno, que utiliza solución de baja fuerza iónica (LISS), la de antiglobulina indirecta, la de aglutinación en gel, la inhibición de la aglutinación, la hemólisis y la adherencia de eritrocitos en fase sólida. Se abordan los problemas que afectan a la reacción de aglutinación entre el antígeno y el anticuerpo; para una mejor comprensión la reacción de aglutinación se subdivide en su primera y segunda etapa. En la primera etapa los factores que se analizan son concentración de antígeno y anticuerpo, pH, temperatura, fuerza iónica y tiempo de incubación; en la segunda etapa la característica del anticuerpo, localización y número de sitios antigénicos, fuerzas que mantienen la distancia entre los eritrocitos, uso de la albúmina bovina, uso de enzimas, efecto de dosis y efecto de moléculas con carga positiva.

Awide range of procedures for the detection and identification of red cell antibodies in vitro has been developed in Immunohematology. Therefore, it is made a review of the techniques and methods used with this aim, such as the method using erythrocytes pretreated with proteolytic enzimes and the techniques of Polibreno that utilize low ionic force solution (LIFS), the indirect antiglobulin test, the gel agglutination test, the agglutination inhibition test, hemolysis and the solid phase erythrocyte adherence test. The problems affecting the agglutination reaction between the antigen and the antibody are also dealt with. The agglutination reaction is subdivided into its first and second phase for a better understanding. In the first phase, the antigen and antibody concentration, pH, temperature, ionic force and incubation time are analyzed. The characteristic of the antibody, localization and number of antigenic sites, forces maintaining the distance among the erythrocytes, use of bovine albumin, use of enzimes, dose effect and effect of molecules with positive charge are studied in the second phase.