La(SSB)

Product Information

Sjögren's syndrome (SS) is a common systemic autoimmune inflammatory disorder characterised by lymphocyte-mediated destruction of exocrine glands leading to diminished or absent glandular secretion¹. SS may present as a primary disease or in association with other systemic autoimmune diseases (referred to as secondary SS).

Autoantibodies to the La(SSB) antigen are present in the serum of 40 – 70% of patients with SS^1,2. The presence of anti-La(SSB) autoantibodies usually coincides with the presence of anti-Ro(SSA) autoantibodies², however the anti-La is more specific for SS than anti-Ro³. Anti-La autoantibodies have also been reported to be present in other clinical conditions, most notably in the sera of mothers of infants with neonatal lupus syndrome2, and in 45% of SLE patients².

La(SSB) antigen is found in both the nucleus and cytoplasm. It binds to nascent RNA polymerase III transcripts and has important roles facilitating transcriptional termination, maturation of the RNA transcripts, and reinitiation of this enzyme^3-6.

La(SSB) is a 46-48 kDa highly phosphorylated protein. At least 8 isoelectric forms (pI range 6 to 7) have been identified⁷.

The amino acid sequences of both human and bovine La(SSB) antigen have been determined by cDNA cloning and sequencing^8,9. Comparison of the two amino acid sequences shows a total of 95% identity. Three regions of the La molecule (amino acids 1-107, 111-242 and 346-408) are thought to contain the major epitopes reactive with human anti-La sera⁹. The broad cross-reactivity of patient sera with La(SSB) from diverse mammalian species indicates the presence of conserved epitopes⁸.

The use of bovine La(SSB) antigen for the detection of human anti-La(SSB) antibodies has been described^10,11.

Clinical Indications

Sjögren’s syndrome
Systemic Lupus Erythematosus
Neonatal Lupus syndrome

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MSDS

References

1. Aziz, E. et al. (1992) Aust. NZ J. Med. 22, 671
2. Yoshimi, et al. (2012) Clin. Dev. Immunol. 2012, 2012:606195
3. Franceschini, F. & Cavazzana, I. (2005) Autoimmunity 38, 55
4. Gottlieb, & Steitz, J.A. (1989) EMBO J. 8, 841,851
5. Gottlieb, & Steitz, J.A. (1989) EMBO J. 8, 841,851
6. Maraia, J. et al. (1994) Mol. Cell Biol. 14, 2147
7. Francoeur, M. et al. (1985) Mol. Cell Biol. 5, 586
8. Chan, K.L. et al. (1989) Nucleic Acids Res. 17, 2233
9. Chambers, C. et al. (1988) J. Biol. Chem. 263, 18043
10. Chan, K.L. & Tan, E.M. (1987) J. Exp. Med. 166, 1627
11. Zhang, & Reichlin, M. (1996) Arthritis Rheum. 39, 522