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Regulation of major histocompatibility complex (MHC) class II antigen expression by cytokines has been suggested to play a major role in the initiation and propagation of immune and autoimmune processes. The analysis of class II gene regulation benefits greatly from the existence of mutants with defects in regulatory factors. We report the establishment of a subclone of the human monocytic cell line U937, termed C119/9, with unusual cytokine regulation of MHC class II expression. In contrast to the parental U937 cell line, only tumor necrosis factor (TNF)-alpha, and not interferon (IFN)-gamma induces the expression of MHC class II antigens on C119/9 cells, and paradoxically, this induction was inhibited almost completely by IFN-gamma. The HLA-DR induction is controlled at the transcriptional level by the first 150 bp of the class II promoter which contains all the class II consensus elements. Both HLA-DR and -DQ mRNA are induced by TNF-alpha treatment, and both are diminished upon co-treatment with TNF-alpha and IFN-gamma. This antagonism between TNF-alpha and IFN-gamma seem to be restricted to MHC class II genes. This subline of U937 cells may be useful in further studies of MHC class II regulation.

Two hybridoma antibodies (VEP8 and VEP9) raised against the promyelomonocytic leukemia cell line HL60 have previously been shown to distinguish human granulocytes and monocytes from other cells of the peripheral blood. We report here that both antibodies recognize the carbohydrate structure 3-fucosyl-N-acetyllactosamine with the following sequence: (formula; see text) This structure is the same as that recognized by a hybridoma antibody against mouse teratocarcinoma cells (anti-SSEA-1) which recognizes an early embryonic antigen in the mouse. Until recently this carbohydrate structure was considered to be rare among glycoproteins and glycosphingolipids. However, there is a growing list of human and animal glycoproteins in which this sequence has been detected by chemical and immunochemical methods. In this article we survey this information and discuss how this and other carbohydrate structures behave as differentiation- or tumor-associated antigens.