Induction and Function of FcεRII on YT Cells; Possible Role of ADF/Thioredoxin in FcεRII Expression

The regulation of low-affinity Fc receptor for lgE (FcγRII) and the characteristics of both membrane and soluble forms of FcγRII were studied using YT cell line. We found that YT cells, a human NK like cell line, expressed FcγRII after IL-1 stimulation. Cross-linking of FceRII on IL-1-stimulated YT cells as well as the transfectant of FcεRII-cDNA (YTSER) resulted in the up-regulation of IL-2Rα (p55/Tac). A 59 kDa protein phosphorylated at tyrosine residues was co-immunoprecipitated with FceRII from YTSER lysate using H107 anti-FcεRII mAb. YTSER not only expressed FceRII on their surface but also secreted soluble form of FcεRII (sFcεRII/sCD23; IgE binding factor). Affinity purification revealed that sFcεRII released from YTSER is heterogeneous and consisted of several proteins differing in molecular weight. Both EBV + B cells and HTLV-1+ T cells are high producers of ATL derived factor (ADF)/ thioredoxin (TRX) and express FcεRII and IL-2Rα respectively. To clarify the mechanism of FcεRII and IL-2Ra induction by ADF/TRX, we examined the effect of ADF/TRX on the bindability of nuclear factor κB (NF-κB), which is known to regulate IL-2Rα gene expression. In the gel shift assay, ADF/TRX was shown to enhance the bindability of NF-κB to its responsive element.