RNASE1 and synovial sarcoma: To investigate the effect of RNase on the FcγR-stimulating activity of RNA-containing ICs, we generated recombinant human RNase1 fused with the IgG1 Fc portion (RNase-Fc) in which the FcR binding sites were mutated, as RNase-Fc has also been used in previous clinical trials for SLE and SS (10, 21).