Inter- and intra-subject variation of the suppression of mitogen-induced proliferation of human lymphocytes by cyclosporin-A: reduction of response with delayed addition may be relevant to timing of therapy

Detection and quantification of cyclosporine in body fluids using an interleukin-2 reporter-gene assay

Different assays are employed to monitor the concentration of immunosuppressive drugs in biological fluids. None of these methods gives direct and precise information on the actual level of immunosuppression in the patient. Here we describe the use of an interleukin-2 (IL-2) reporter-gene assay (IL-2 RGA) to monitor the concentrations of immunosuppressants in body fluids. This assay is based on a chimeric gene construct in which the human IL-2 promoter drives the expression of a reporter gene. Upon mitogenic stimulation the reporter gene is expressed and can be easily quantified. The assay is very sensitive and selective for immunosuppressive compounds inhibiting IL-2 gene expression such as cyclosporine (CsA) and FK506, their active metabolites and derivatives, but not for others such as rapamycin. High reproducibility, fast performance time, and high capacity are additional characteristics of the assay. The assay was developed to monitor immunosuppressive drug levels in human volunteers or in animals receiving CsA analogues as the only immunosuppressive drugs. This assay is sensitive to CsA or ascomycin/FK506 analogues and metabolites, for which there are presently no specific monoclonal antibodies available. The IL-2 reporter-gene assay may be more suitable than other in vitro systems such as MLR or mitogen stimulated PBMC which were previously used to study the immunosuppressive activity of drugs in body fluids.

T lymphocytes increase the synthesis of esterified cholesterol in human monocyte-derived macrophages by activation of the scavenger pathway

Immunohistochemical analyses have shown the presence of T lymphocytes (T-cells) in atherosclerotic places in addition to macrophages and smooth muscle cells. To elucidate the role of T-cells in the formation of atherosclerotic lesions, we studied whether T-cells can stimulate the scavenger pathway and promote esterified cholesterol (EC) synthesis by [14C]oleate incorporation in macrophages. Macrophages and T-cells were co-cultured in two ways. In one culture, macrophages were in direct contact with T-cells (direct contact form). In the other, macrophages and T-cells were separated by Transwell membrane, but shared the same culture medium via the membrane (indirect contact form). Based on the incorporation of [14C]oleate into EC, macrophages strikingly increased EC synthesis in both forms of co-culture. This increase was proportional to the number of T-cells present and was inhibited by cyclosporin A. When macrophages were co-cultured indirectly in contact with T-cells in the presence of AcLDL for 24 h, and the T-cells were subsequently removed, EC synthesis in macrophages increased. However, this increase was not observed in macrophages that were rinsed twice with PBS. When macrophages, previously incubated with AcLDL for 24 h, were co-cultured indirectly in contact with T-cells for 24 h, the medium were prepared as activated T-cell-conditioned medium (aTCM). EC synthesis in macrophages cultured with aTCM increased. The ability of aTCM to increase EC synthesis disappeared upon repeated freezing/thawing, boiling and trypsin treatment. T-cells (indirect contact form) and aTCM similarly increased AcLDL-binding and -degradation in macrophages. These results indicated that T-cells secreted an active substance(s), protein in nature, which could activate the scavenger pathway and increase EC synthesis in macrophages. These observations suggest that T-cells can promote the uptake of modified lipoproteins by macrophages to induce foam cell-formation.