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Arthritis Rheum. 1992 Jun;35(6):663-6.

Restricted epitope recognition by precipitin-negative anti-La/SS-B-positive sera.

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1
Department of Clinical Immunology, Flinders Medical Centre, Bedford Park, South Australia.

Abstract

OBJECTIVE:

To determine whether anti-La/SS-B-positive sera that are precipitin negative show a distinct B cell epitope pattern.

METHODS:

Serum reactivity was tested with recombinant La/SS-B fusion proteins.

RESULTS:

Among the 18 precipitin-negative anti-La/SS-B-positive sera, reactivity was confined to the full-length recombinant protein (La33.3) in 8 (44%); 5 of 18 (28%) reacted only with La33.3 and with the first 107 N-terminal amino acids (LaA), and 4 (22%) reacted with La33.3, LaA, and the middle region of the La molecule (LaC; amino acids 111-242). One serum reacted with La33.3 and LaC. None of the 18 precipitin-negative sera was positive on a carboxy-terminal fragment (LaL2/3; amino acids 346-408). In contrast, all 26 precipitin-positive anti-La/SS-B-positive sera reacted with La33.3, LaA, and LaC, and 92% reacted with LaL2/3. Rheumatoid factor and serum IgG levels were significantly lower in the precipitin-negative group, providing further evidence of a distinct serologic subset.

CONCLUSION:

The restricted epitope recognition by these sera may explain the lack of precipitin formation and may represent an early autoantibody response to La/SS-B.

PMID:
1376123
DOI:
10.1002/art.1780350609
[Indexed for MEDLINE]

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