M Iwata

T Cell Factors Involved in the Regulation of the IgE Synthesis

The IgE-potentiating and IgE-suppressive factors share a common structural gene and therefore a common polypeptide chain, and their biologic activities are decided by a post-translational glycosylation process. Under physiological conditions, this process is controlled by two T cell factors, i.e., the glycosylation-enhancing factor (GEF) and glycosylation-inhibiting factor (GIF). GIF is a fragment of phosphorylated lipocortin and has immunosuppressive effects. Repeated injections of this lymphokine into antigen-primed mice switched their T cells from the formation of IgE-potentiating factor to the formation of IgE-suppressive factor and facilitated the generation of antigen-specific suppressor T cells, which form antigen-specific GIF upon antigenic stimulation. The antigen-specific GIF suppressed the antibody response in a carrier-specific manner and has properties similar to antigen-specific suppressor T cell factors.

Role of Glycosylation Inhibiting Factor (GIF), a Phospholipase Inhibitory Protein, in the Generation of Antigen-Specific Suppressor T Cells

Previous experiments on the isotype-specific regulation of the IgE antibody response revealed T cell factors which have affinity for IgE and either enhance or suppress the IgE response (1). The major differences between the IgE-potentiating factors (PF) and IgE-suppressive factors (SF) are carbohydrate moieties in the molecules. The IgE-potentiating factors bind to lentil lectin and Con A, suggesting that the factors contain N-linked, mannose-rich oligosaccharide. In contrast, IgE-suppressive factors have no affinity for these lectins but bound to peanut agglutinin (2). Recent experiments in collaboration with Drs. Moore and Martens in DNAX Institute of Molecular Biology indicate that IgE-PF and IgE-SF share a common structural gene (3). Transfection of COS 7 monkey kidney cells with the cDNA clone 8.3, which encodes the rodent IgE-binding factor (4) resulted in the formation of IgE-PF, whereas the transfection of the same cells with the same cDNA clone in the presence of tunicamycin resulted in the formation of IgE-SF.