The use of interferon-γ-treated U937 cells in chemiluminescence assays to detect red cell, platelet and granulocyte antibodies of potential clinical significance

Abstract

The chemiluminescent (CL) response of interferon-gamma-treated U937 (IFN-U937) cells to sensitized target cells has been used to detect red cell, platelet and granulocyte antibodies. A clone of U937 cells was selected which expressed Fc receptor I (Fc gamma RI) and which, after incubation with IFN-gamma for 72 h, was capable of generating high levels of lucigenin-enhanced CL. The CL responses of IFN-U937 cells and peripheral blood human monocytes to sensitized red cells, platelets or granulocytes were then compared. Assays using monocytes or IFN-U937 cells were of comparable sensitivity for detection of antibodies against all three types of target cell. In addition, the use of IFN-U937 cells reduced interassay variation and simplified assay performance. The potential clinical usefulness of these CL assays was suggested by the ability of both monocytes and IFN-U937 cells to respond to red cells, platelets or granulocytes sensitized with sera from pregnant women whose babies had either haemolytic disease of the newborn (HDN), alloimmune thrombocytopenia or alloimmune neutropenia respectively. In addition, monocytes and IFN-U937 cells both responded to red cells sensitized with antibodies against a variety of specificities of assumed (although not documented) clinical significance for blood transfusion recipients. In contrast, monocytes and IFN-U937 cells responded only weakly to red cells sensitized with either anti-D in sera from mothers of babies unaffected by HDN, or with antisera containing high titre antibodies with specificities not normally associated with significantly reduced red cell survival.