La/SS-B Antigen

The La/SS-B antigen is a 47 kD ribonucleic protein that is associated with a spectrum of small RNAs (2). La/SS-B appears to be readily susceptible to proteolysis, resulting in many smaller (42kD, 320, and 270) but still immunoreactive polypeptides (3). It has been shown that the La/SS-B antigen primarily resides in the nucleus (2), and it appears to be associated with RNA polymerase III transcripts (4). It has also been shown that the La/SS-B antigen shows strong conservation across species (5). Anti-La/SS-B autoantibodies were described originally as precipitating autoantibodies in sera of Sjogren’s Syndrome patients and referred to as SjT.(1) A precipitin with the same properties was rediscovered later and termed La and then SS-B. Anti-La/SS-B precipitins are most commonly found in Sjogren’s Syndrome and Systemic Lupus Erythematosus (SLE). The presence of autoantibodies against the La/SS-B antigen has been advocated as a diagnostic aid in Sjogren’s Syndrome patients (6). Autoantibodies against La/SS-B are also commonly found in Systemic Lupus Erythematosus and Subacute Cutaneous Lupus (4). In addition, there appears to be a correlation between anti-La/SS-B and the absence of nephritis in SLE patients. Studies have demonstrated that SLE patients with precipitating Anti-Ro/SS-A antibodies have a high incidence of serious nephritis (53%), while those with both Anti-Ro/SS-A and Anti-La/SS-B have a low (9%) frequency of nephritis (7).

1. Harley JB, Yamagata H, Reichlin M: Anti-La/SS-B antibody is present in some normal sera and is coincident with anti-Ro/SSA precipitins in systemic lupus erythematosus, J Rheum 11, 1984 pg 309-314.
2. Bachman M, Mayet WJ, Shroder HC, et al: Association of La and Ro antigens with intracellular structures in HEp-2 carcinoma Cells. Cell Biology, Vol 83, 1986, pg 7770-7774.
3. Habets WJ, den Brok JH, AM Th. Boerbooms, van de Putte LBA, and van Venrooij WJ: Characterization of SS-B (La) antigen in adenovirus-infected and uninfected HeLa cells. EMBO J. 1983, pg 1625.
4. Harley JB, Rosario MO, Yamagata H, et al: Immunologic and Structural Studies of the Lupus/Sjogren’s Syndrome Autoantigen, La/SSB, with a Monoclonal Antibody: Vol 76, 1985, pg 801-806.
5. Hoch SO, and Billings PB, Agouron Institute: Characterization of the La (SS-B) Antigen From Several Mammalian Sources: J of Immun, Vol 133, 1984, pg 1397-1403.
6. Harley JB, Alexander EL, Bias WB, Fox OF, et al: Anti-Ro/SSA and Anti-La/SSB in Sjogren’s syndrome, Dept of Med, Okla Med Research Foundation. pg 1-35.
7. Reichlin M: Clinical and Immunological Significance of Antibodies to Ro and La in Systemic Lupus Erythematosus. Arthritis and Rheumatism: Vol 25,1982, pg 767-772.
8. Harley JB, Yamagata H, and Reichlin M. Anti-La/SSB Antibody is Present in Some Normal Sera and is Coincident with Anti-Ro/SSA Precipitins in Systemic Lupus Erythematosus: J of Rheumatology, 1984, pg 309-314.