La （SSB） ANTIGEN 
AROTEC_La-SSB_Product_Info.pdf Version/Date: B/04.05.20 
ATL01-02 La （SSB） antigen 0.20 mg 
ATL01-05 La （SSB） antigen 0.50 mg 
ATL01-10 1.0 mg 
_________________________________________________________________________________
Description of the Product
Purified from bovine thymus. After coating onto ELISA plates 
the product will bind autoantibodies to La （SSB）. 
Purity: The La autoantigen （45-50 kDa） is more than 90% 
pure, as assessed by SDS polyacrylamide gel electrophoresis. 
Concentration: 0.1-1.0 mg protein/ml. 
Storage: The product is stabilised with 20% glycerol and 0.1% 
Micr-O-protectTM. Store at -20 o
C or below （long term） or at 
+4o
C （short term）. Avoid repeated freezing and thawing. Mix 
thoroughly before use. 
Clinical and Biochemical Data 
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 secretion1-4. 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 can be detected in the sera of up to 87% of patients 
with primary or secondary SS5,6. The presence of anti-La 
（SSB） autoantibodies usually coincides with the presence of 
anti-Ro （SSA） autoantibodies7
, however the fact that anti-Ro 
autoantibodies are far more common in other rheumatological 
conditions such as systemic lupus erythematosis （SLE） and 
mixed connective tissue disease （MCTD） suggests that anti-La 
is more specific for primary and secondary SS than anti-Ro8,9
. 
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 syndrome10, but also in 10 to 
15% of SLE patients11,12
. 
binds to the oligo（U） 3' termini of nascent 
RNA polymerase III transcripts and facilitates transcriptional 
termination and reinitiation by this enzyme13,-17. It has also 
been reported to function as an ATP-dependent helicase able 
to melt RNA-DNA hybrids18. La （SSB） may be involved in 
other processes as well such as maturation and/or nuclear 
export of RNA polymerase III products and some aspects of 
translation19,20. La （SSB） is a highly phosphorylated protein 
which migrates at about 50 kDa in SDS-polyacrylamide gel 
electrophoresis21. Phosphorylated residues are present at the 
carboxy-terminal part of the protein22. At least 8 isoelectric 
forms （pI range 6 to 7） have been identified23
. 
The amino acid sequences of both human and bovine La 
（SSB） antigen have been determined by cDNA cloning and 
sequencing19,28. Comparison of the two sequences shows 22 
largely conservative amino acid substitutions with 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 sera19,24. The broad 
cross-reactivity of patient sera with La （SSB） from diverse 
mammalian species indicates the presence of conserved 
epitopes25. The use of bovine for the 
detection of human anti-La （SSB） antibodies has been 
described by several authors25-27
.
Methodology
The following is an ELISA procedure which can be used to 
detect anti-La （SSB） autoantibodies in human serum using the 
ATL01 purified autoantigen: 
1. Dilute the purified antigen to 0.5-1.0 µg/ml in PBS （10 mM 
potassium phosphate, pH 7.4, 0.15 M NaCl）. 
2. Coat ELISA plates with 100 µl of diluted antigen per well. 
Cover and incubate 24 hours at +4o
C. 
3. Empty the plates and remove excess liquid by tapping on a 
paper towel. 
4. Block excess protein binding sites by adding 200 µl PBS 
containing 1% BSA per well. Cover and incubate at +4o
C 
overnight. 
5. Empty plates and apply 100 µl of serum samples diluted 
1:100 in PBS / 1% BSA / 1% casein / 0.1% Tween?
 20. 
Incubate at room temperature for 1 hour. 
6. Empty plates and add 200 µl PBS / 0.1% Tween?
 20 per 
well. Incubate 5 minutes then empty plates. Repeat this step 
twice. 
7. Apply 100 µl anti-human IgG-enzyme conjugate 
（horseradish peroxidase or alkaline phosphatase） diluted in 
PBS / 1% BSA / 1% casein / 0.1% Tween?
 20 per well and 
incubate for 1 hour. 
8. Repeat step 6. 
9. Add enzyme substrate and stop the reaction when 
appropriate. 
10. Read absorbance in an ELISA spectrophotometer. 
References 
1. Molina, R. et al. （1986） Am. J. Med. 80, 23 
2. Bloch, K.J. et al. （1965） Medicine 44, 187 
3. Fox, R.I. et al. （1986） Arthritis Rheum. 29, 577 
4. Aziz, K.E. et al. （1992） Aust. NZ J. Med. 22, 671 
5. Manoussakis, M.N. et al. （1986） Scan. J. Rheumatol. 61, 89 
6. Harley, J.B. et al. （1986） Arthritis Rheum. 29, 196 
7. Craft, J.E. & Hardin, J.A. （1987） J. Rheumatol. 14 S13, 106 
8. St. Clair, E.W. （1992） Rheum. Dis. Clin. N. America 18, 359 
9. Harley, J.B. （1989） J. Autoimmun. 2, 383 
10. Buyon, J.P. et al. （1989） J. Clin. Invest. 84, 627 
11. Reichlin, M. （1986） J. Clin. Immunol. 6, 339 
12. Wiascewk, C.A. & Reichlin, M. （1982） J. Clin. Invest. 69, 835 
13. Stefano, J.E. （1984） Cell 36, 145 
14. Gottlieb, E. & Steitz, J.A. （1989） EMBO J. 8, 841 
15. Gottlieb, E. & Steitz, J.A. （1989） EMBO J. 8, 851 
16. Maraia, R.J. et al. （1994） Mol. Cell Biol. 14, 2147 
17. Maraia, R.J. （1996） Proc. Natl. Acad. Sci. USA 93, 3383 
18. Bachmann, M. et al. （1990） Cell 60, 85 
19. Chambers, J.C. et al. （1988） J. Biol. Chem. 263, 18043 
20. Bachmann, M. et al. （1989） Mol. Cell Biochem. 85, 103 
21. Pruijn, G.J.M. （1994） Man. Biol. Markers Dis. （Kluwer Acad. 
 Publ.） B4.2/1-14 
22. Pfeifle, J. et al. （1987） Biochim. Biophys. Acta 928, 217 
23. Francoeur, A.M. et al. （1985） mol. Cell Biol. 5, 586 
24. McNeilage, L.J. （1990） J. Immunol. 145, 3829 
25. Chan, E.K.L. & Tan, E.M. （1987） J. Exp. Med. 166, 1627 
26. Zhang, W. & Reichlin, M. （1996） Arthritis Rheum. 39, 522 
27. Chan, E.K.L. et al. （1986） J. Immunol. 136, 3744 
28. Chan, E.K.L. et al. （1989） Nucleic Acids Res. 17, 2233 
Micr-O-protect is from Roche Diagnostics GmbH （Mannheim, 
Germany）. 
Tween?
 20 is a registered trademark of ICI Americas Inc. 
NOTE: No patented technology has been used by AroTec 
during the preparation of this product.