Stephen Stux

Modulation of allogeneic stimulation in man. I. Characterization of an in vitro induced suppressor macrophage population

Cultured human peripheral blood mononuclear cells suppressed the allogeneic response of fresh autologous lymphocytes. This suppressor activity developed gradually over a period of one week. The cells primarily responsible for this effect were enriched by Ficoll density gradient centrifugation. It was found that the suppressor cell is a large, low density nylon wool adherent, radioresistant, phagocytic, and nonspecific esterase positive mononuclear cell. Moreover, these cells did not form E rosettes and were Fc positive. Electron microscopy confirmed that suppressor cells were macrophage like. Suppressor activity was not due to cytotoxicity, crowding, or steric hinderance by the cultured cells. The suppressor macrophage population did not appear to inhibit the allogeneic response via prostaglandin or arginase release, or interfere with the tritiated thymidine uptake by release of endogenous thymidine. The above system is viewed as an in vitro model of immune regulation by suppressor macrophages, in the context of allogeneic response.

Platelet HLA Typing and Cross-Matching by a Direct Microcytotoxic Assay

Abstract: Carboxyfluoresceindiacetate‐labelled platelets can be used in direct microcytotoxic assays for the purpose of typing platelets for a number of antigenic determinants, such as HLA and β‐2 microglobulin. The assay when used in direct platelet cross‐matching, where thrombocytopenic patient sera were screened, resulted in the uncovering of many extra‐positive and weakly positive cross‐matches not identified by the lymphocyte cross‐match. The simplicity and rapidity of this new method makes it an attractive alternative for future use in research and clinical studies.