Human Anti-La/SS-B polyclonal antibody for ELISA. The La/SS-B antigen is a 47 kD ribonucleic protein that is associated with a spectrum of small RNAs. La/SS-B appears to be readily susceptible to proteolysis, resulting in many smaller (42kD, 320, and 270) but still immunoreactive polypeptides. It has been shown that the La/SS-B antigen primarily resides in the nucleus, and it appears to be associated with RNA polymerase III transcripts. It has also been shown that the La/SS-B antigen shows strong conservation across species. Anti-La/SS-B autoantibodies were described originally as precipitating autoantibodies in sera of Sjogren's Syndrome patients and referred to as SjT.