Deposition and spectral performance of an inhomogeneous broadband wide-angular antireflective coating.

Gradient index coatings and optical filters are a challenge for fabrication. In a round-robin experiment, basically the same hybrid antireflection coating for the visible spectral region, combining homogeneous refractive index layers of pure materials and linear gradient refractive index layers of material mixtures, has been deposited. The experiment involved three different deposition techniques: electron-beam evaporation, ion-beam sputtering, and radio frequency magnetron sputtering. The material combinations used by these techniques were Nb(2)O(5)/SiO(2), TiO(2)/SiO(2), and Ta(2)O(5)/SiO(2), respectively. The spectral performances of samples coated on one side and on both sides have been compared to the corresponding theoretical spectra of the designed profile. Also, the reproducibility of results for each process is verified. Finally, it is shown that ion-beam sputtering gave the best results in terms of deviation from the theoretical performance and reproducibility.

In vitro stimulation of human endothelial cells by sera from a subpopulation of high-percentage panel-reactive antibody patients.

We have studied a serum activity that enhances in vitro ICAM-1 expression by human endothelial cells (EC) and report that this activity can be found in approximately 8% of pretransplant serum samples from individuals with a history of high %PRA. Hence, most high %PRA sera lack this activity, and, furthermore, mixing these negative sera does not result in an active serum pool. In patients with active serum, the ICAM-1 enhancing activity is found only sporadically, despite the continuous detection of endothelial-reactive antibodies. Absorption of Ig from a high %PRA serum reduced ICAM-1 enhancing activity, as well as endothelial-reactive antibodies. However, enhancing activity can sometimes be observed in sera that lack detectable endothelial-reactive antibodies, and none of several patient sera with defined MHC class I-specific alloantibodies displayed ICAM-1 enhancing activity. Together, these data suggest that ICAM-1 enhancing activity may not necessarily be mediated by anti-MHC alloantibodies. In addition to influencing this expression, ICAM-1 active patient sera also influence EC expression of VCAM-1 and MHC class I, but not MHC class II molecules, a pattern that is similar to that stimulated by TNF alpha. However, coincubation of EC with active serum plus soluble TNF receptor did not block the endothelial phenotypic changes, despite the ability of the soluble receptor to completely abrogate endothelial changes induced by TNF alpha. IFN gamma also increases endothelial ICAM-1 expression, but has response kinetics different from that of active serum. Interestingly, brief treatment of endothelial cells with IFN gamma greatly increased the amount of IgG bound from the active sera by EC. We conclude that some pretransplant patients occasionally express an activity in their serum that influences EC expression of several adhesion molecules, including ICAM-1, VCAM-1, and MHC class I. This activity may be associated with alloantibodies, but is independent of MHC class I-reactive antibodies, circulating TNF alpha, or IFN gamma. The relevance of a serum-borne component capable of activating EC is discussed.

Differential effects of gallium nitrate on T lymphocyte and endothelial cell activation.

The immunosuppressive agents used clinically to prevent allograft rejection exert their effects by interfering with antigen-dependent T cell activation, endothelial cell function, or both. Gallium nitrate (GN) is immunosuppressive both in vitro and in vivo, and has potential for clinical use in transplant recipients. Therefore, we analyzed the influence of GN on gonadal vein endothelial cell (GVEC) and T cell activation. GVEC were stimulated with IFN gamma or TNF alpha in the presence or absence of GN, and tested for changes in levels of MHC class I, MHC class II, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 expression. GN did not interfere with the baseline or cytokine-enhanced expression of these molecules. Rather, it increased the expression of intercellular adhesion molecule-1 on GVEC, and this effect was further augmented in the presence of IFN gamma. In contrast, GN inhibited T cell proliferation stimulated by allogeneic GVEC or allogeneic monocytes in a dose-dependent manner. In transwell experiments, GN blocked the induction of MHC class II expression on isolated GVEC caused by alloactivated T cells, but not by recombinant IFN gamma. This suggests that GN can interfere indirectly with inflammatory responses of endothelial cells by interfering with local T cell activation and lymphokine production. Once lymphokines are produced, GN does not interfere with their effects on endothelial cells. GN is thought to act through transferrin receptors, but GVEC, unlike T cells, do not increase their expression of transferrin receptors, after stimulation with cytokines. This may explain their relative lack of sensitivity to GN. In general, GN appears to stimulate endothelial cells but suppress T cells. This paradoxic effect suggests that therapy with GN may enhance T cell-independent inflammatory responses, such as cellular infiltration and repair of tissue damage, while suppressing T cell-dependent responses, such as T cell-mediated tissue destruction and allograft rejection.

Kinetic and energetic parameters of imipramine binding to monoclonal antibodies as measured by fluorescence spectroscopy.

Monoclonal antibodies which bind small drugs are useful for the study of the interactive forces involved in antibody-ligand complexation. Detailed understanding of these supramolecular forces requires a careful examination of structural and thermodynamic parameters of the interacting molecules. Fluorescence spectroscopy techniques are very useful in this regard. We report here, the kinetic and energetic parameters of four monoclonal antibodies made against the tricyclic antidepressant imipramine. These monoclonal antibodies were found to possess high to very high binding affinity constants, ranging from 10(7) to 10(10) M-1, and caused fluorescence quenching or enhancement of a fluorescein labelled imipramine. The dissociation rates of the fluorescent ligand from the complexes were measured at different temperatures in order to provide some insight regarding the kinetic and energetic (thermodynamic) parameters of the antibody-ligand binding interactions.