Accessory Cell Function of Human Vascular Endothelial Cells in Pokeweed-Mitogen-Stimulated Immunoglobulin Production by Peripheral Blood Lymphocytes

Abstract

The possibility that human vascular endothelial cells (EC) can function as accessory cells for pokeweed mitogen (PWM)-induced immunoglobulin synthesis by peripheral blood lymphocytes was examined. Adherent cells (AC) were vigorously depleted from peripheral blood mononuclear cells (PBMC) and PBMC were cocultured with or without various numbers of EC or AC in the presence of PWM. EC which had been treated with interferon-gamma (IFN-gamma) expressed HLA class II antigens on the surface and promoted both IgM and IgG production by lymphocytes as effectively as monocytes did. Nontreated EC also enhanced immunoglobulin synthesis, but less effectively. Pretreatment of EC with monoclonal anti-HLA class II antigen antibody suppressed the accessory cell function of EC. These results indicate that EC have the ability to function as sufficient accessory cells in the mitogen-induced in vitro immunoglobulin synthesis, and that this ability was closely related to the expression of HLA class II antigen. Under the circumstance of an inflammatory response where IFN-gamma would exist, the accessory cell function of EC would be enhanced and would modify the immune response of immunocompetent cells.