Induction and amplification of T-lymphocyte proliferative responses to periodate and soybean agglutinin by human adult vascular endothelial cells

Accessory function of endothelial cells in anti-CD3-induced T-cell proliferation: synergism with monocytes

Monoclonal antibodies to CD3 can induce proliferation of resting T cells. In vitro this effect is dependent on the presence of monocytes. They serve as accessory cells providing a co-stimulatory signal after cross-linking of the antibody-coated TcR/CD3 complex by the Fc receptor on the monocytes. We have studied whether endothelial cells can replace monocytes with regard to this function. Highly purified T-cell preparations were cultured in the presence of anti-CD3 antibody, purified monocytes, and human umbilical vein endothelial cells. Anti-CD3 and endothelial cells alone were unable to support T-cell proliferation, due to lack of FcR expression. Addition, however, of as few as 1000 FcR+ monocytes (0.8% of the number of T cells present) to a coculture of T cells and endothelial cells (EC) in the presence of soluble anti-CD3 resulted in a strong proliferation of T cells. When anti-CD3 was presented in an immobilized form (coated to the culture well or to Sepharose beads), or when phytohaemagglutinin was added to the culture as a cross-linking agent, EC could support T-cell proliferation in the absence of any monocytes. We conclude that EC by themselves cannot support the proliferation of pure T cells induced by soluble anti-CD3, but are potent generators of the co-stimulatory signal(s). They provide a suitable starting material to further define this co-stimulatory activity.

Monocyte-T lymphocyte interaction for regulation of insulin receptors of the activated T lymphocyte

During activation the lymphocyte attains functional insulin receptors with precise regulation, a consequence of insulin concentration manipulations. These studies test the hypothesis that insulin receptor (+) monocytes monitor insulin concentrations, so instructing the T lymphocytes. Monocyte-enriched populations were incubated with insulin (0-10(-6) M) followed by co-culture with T lymphocytes and an activating stimulus. A dose-related fall in T lymphocyte insulin receptor binding was observed that was specific for the monocyte as the signalling cell and for insulin as the signal received. Monocytes from normal volunteers during a euglycemic, hyperinsulinemic clamp were cultured with T lymphocytes and an activating stimulus. A decline in specific insulin receptor binding on T lymphocytes was observed, which Scatchard analysis demonstrated to be a consequence of reduction in receptor numbers. These studies demonstrate that the receptor (+) monocyte perceives the concentration of insulin and passes this information to T lymphocytes regulating the number of activation-induced insulin receptors. The interplay between the monocyte and T lymphocyte parallels the interaction of these cell types for recognition of antigen.

Adhesion of T lymphocytes to human endothelial cells is regulated by the LFA-1 membrane molecule

Human T lymphocyte adhesion to human endothelial cells is the initial event in T cell migration to areas of extravascular inflammation. The molecular basis for T cell-endothelial cell adhesion was investigated using two different cell-cell adhesion assays: a) a fluorescein cell-cell adhesion assay using nonadherent endothelial cells and fluorescein-labeled T lymphocytes, and b) a radionuclide cell-cell adhesion assay using adherent endothelial cells and 51Cr-labelled T cells. Both assay systems demonstrated comparable quantitative assessment of cell-cell adhesions. The assays were performed at 22 degrees C and adhesions were maximal at 30 min. The results of these adhesion assays confirmed previous reports that T cells adhere to endothelial cells. In addition, we have shown that T cells adhere only marginally to foreskin fibroblasts or bone marrow derived fibroblasts. T cell-endothelial cell adhesions were significantly stronger than either monocytes or B lymphoblastoid cells adhesion to endothelial cells. To demonstrate the molecular mechanisms involved in regulating T cell-endothelial cell adhesions, a panel of function-associated monoclonal antibodies (MAb) were tested for their ability to inhibit T cell adhesion. MAb reactive with the leukocyte surface glycoprotein LFA-1 significantly inhibited T cell-endothelial cell adhesions in both assay systems. In contrast, MAb directed at other surface antigens did not inhibit T cell adhesion. The involvement of the LFA-1 glycoprotein in T lymphocyte adhesion to endothelial cells suggest that the LFA-1 molecule may be important in the regulation of leukocyte interactions.

Recurrent thrombotic microangiopathy in a renal allograft. Case report and review of the literature

Thrombotic microangiopathy in a renal allograft may either reflect a recurrence of the patient's original disease, i.e., thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, or more commonly may be a manifestation of allograft rejection. This report describes a patient in whom irreversible renal failure developed during thrombotic thrombocytopenic purpura. Two years later while her condition was in clinical remission, she received a 2 DR-matched cadaveric allograft. Nineteen days following transplantation, thrombotic microangiopathy developed in the graft with eventual loss of allograft function despite vigorous plasmapheresis therapy. Multiple factors in addition to possible recurrent disease that may have contributed to this event were identified. The literature on thrombotic microangiopathy and renal transplantation is reviewed.