Objective. The anti-La/SSB response to major B cell epitopes of La/SSB
can be blocked by an active idiotypic/antiidiotypic network, which can
be identified using synthetic complementary epitopes deduced from the
sequence of the major B cell epitopes of the molecule. This study
evaluated the role of this network in pregnant women with anti-Ro/SSA
and/or anti-La/SSB antibodies in the development of neonatal lupus
syndrome (NLS).
Methods. Sixty-three serum samples collected from
anti-Ro/anti-La-positive women during pregnancy or within 6 months after
delivery were obtained from the Research Registry for Neonatal Lupus and
the PR Interval Dexamethasone Evaluation study. These samples, as well
as 30 sera from healthy individuals, were tested in a blinded manner by
enzyme-linked immunosorbent assay against, synthetic peptides
corresponding to major B cell epitopes and complementary epitopes of
La/SSB.
Results. Sera from mothers giving birth to a healthy child and having no
history of a child with NLS exhibited higher antiidiotypic antibody
activity compared with mothers carrying a child with NLS (P < 0.0001) or
mothers giving birth to a healthy child but who previously gave birth to
a child with NLS (P 0.0151). Sera from mothers of healthy children,
which exhibited no apparent epitope activity against amino acids
349-364, revealed a significantly greater frequency of hidden
anti-349-364aa epitope responses, blocked by antiidiotypic antibodies,
as compared with sera from women pregnant with an affected child (P =
0.0094).
Conclusion. The presence of antiidiotypic antibodies to autoantibodies
against La/SSB may protect the fetus by blocking pathogenic maternal
autoantibodies. Testing for these antiidiotypic responses may be useful
in predicting a decreased risk of NLS