Identification and characterization of two new soluble nuclear antigens reactive with sera of patients with connective tissue diseases.

Two antigens, temporarily referred to as MU and TM antigens after the original serum, that are closely related to the nucleolus have been identified in the nuclear soluble extract. Both antigens reacted with the sera of a small number of patients with various connective tissue diseases, and both were different from antigens described previously in these disorders. MU antigen was sensitive to the digestion with RNase and trypsin, and was shown to be equivalent to the nuclear ribosomal components in the nuclear extract. TM antigen was resistant to the digestion with RNase and trypsin, and was localized in the nucleolus and extranucleolar portion of nuclei, but the precise nature of TM has not been established.