DOI Page / Citation link:
https://doi.org/10.11588/diglit.48120#0110
92 Molecular and Cell Biology of Autoantibodies and Autoimmunity
idiotype, 16/6, that has recurred on several different anti-DNA monoclonal an-
tibodies, and on immunoglobulins in both the serum and tissue lesions of SLE
patients. Both its heavy and light chain variable regions have been sequenced. An-
tibody 21/28 does not carry the 16/6 idiotype, but the center of its heavy chain
CDR3 is identical to that in 18/2. Its VH gene is from a different family than
that of 18/2, but both proteins have similar amino acid sequences in and adjacent
to the heavy chain CDR1. To prepare serological reagents that could detect recur-
rence of related primary structures in other immunoglobulins, we have synthesiz-
ed three peptides with sequences corresponding to the light chain CDR 3 of an-
tibody 18/2 and to the heavy chain CDR1 and CDR 3 of antibody 21/28. Rabbits
were immunized with peptide-KLH conjugates of each of the peptides. Each an-
tiserum reacted specifically with the immunizing peptide in direct and competitive
ELISA, and with homologous intact IgM on dot blots. Anti-18/2 L-chain CDR 3
reacted with the 18/2 light chain on a Western blot, and detected no crossreacting
molecules in a dot-blotted panel of 10 other human IgM immunoglobulins. An-
ti-21/28 H-CDR3 reacted with both 21/28 and 18/2 proteins, which share se-
quence identity in this region, but it had the unpredicted property of reacting only
with intact protein and not with heavy chain on a Western blot. A monoclonal
murine antibody to the same peptide had the same property. The peptide is
recognized in a conformation that occurs in native structure, but not in protein
exposed to heat, SDS and mercaptoethanol. The third serum reacted with heavy
chain on a Western blot, and cross-reacted with the heavy chain of 18/2, which
has a similar sequence in this region even though it is encoded by a VH gene of
a different family. The three anti-peptide sera are being tested as reagents for
detection of recurrent primary structures.
Immunological Characterization of IgM Class Autoantibodies Against
Sm-Antigenic B7B and D Polypeptides of U Small Nuclear
Ribonucleoproteins (snRNPs)
Y. Takeda, G. S. Wang, and G. C. Sharp
University of Missouri, Columbia, MO 65212, USA
IgG anti-Sm autoantibodies are known to react with epitope(s) shared by B'/B
and D polypeptides of U snRNPs. With respect to the reactivities of IgM an-
tibodies, only a few studies have been done at the polypeptide level. In this study,
we investigated more detailed characteristics of IgM antibodies against Sm-anti-
idiotype, 16/6, that has recurred on several different anti-DNA monoclonal an-
tibodies, and on immunoglobulins in both the serum and tissue lesions of SLE
patients. Both its heavy and light chain variable regions have been sequenced. An-
tibody 21/28 does not carry the 16/6 idiotype, but the center of its heavy chain
CDR3 is identical to that in 18/2. Its VH gene is from a different family than
that of 18/2, but both proteins have similar amino acid sequences in and adjacent
to the heavy chain CDR1. To prepare serological reagents that could detect recur-
rence of related primary structures in other immunoglobulins, we have synthesiz-
ed three peptides with sequences corresponding to the light chain CDR 3 of an-
tibody 18/2 and to the heavy chain CDR1 and CDR 3 of antibody 21/28. Rabbits
were immunized with peptide-KLH conjugates of each of the peptides. Each an-
tiserum reacted specifically with the immunizing peptide in direct and competitive
ELISA, and with homologous intact IgM on dot blots. Anti-18/2 L-chain CDR 3
reacted with the 18/2 light chain on a Western blot, and detected no crossreacting
molecules in a dot-blotted panel of 10 other human IgM immunoglobulins. An-
ti-21/28 H-CDR3 reacted with both 21/28 and 18/2 proteins, which share se-
quence identity in this region, but it had the unpredicted property of reacting only
with intact protein and not with heavy chain on a Western blot. A monoclonal
murine antibody to the same peptide had the same property. The peptide is
recognized in a conformation that occurs in native structure, but not in protein
exposed to heat, SDS and mercaptoethanol. The third serum reacted with heavy
chain on a Western blot, and cross-reacted with the heavy chain of 18/2, which
has a similar sequence in this region even though it is encoded by a VH gene of
a different family. The three anti-peptide sera are being tested as reagents for
detection of recurrent primary structures.
Immunological Characterization of IgM Class Autoantibodies Against
Sm-Antigenic B7B and D Polypeptides of U Small Nuclear
Ribonucleoproteins (snRNPs)
Y. Takeda, G. S. Wang, and G. C. Sharp
University of Missouri, Columbia, MO 65212, USA
IgG anti-Sm autoantibodies are known to react with epitope(s) shared by B'/B
and D polypeptides of U snRNPs. With respect to the reactivities of IgM an-
tibodies, only a few studies have been done at the polypeptide level. In this study,
we investigated more detailed characteristics of IgM antibodies against Sm-anti-