DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.48120#0117
Abstracts
99
Immunospecificity and Clinical Association of Autoantibodies in Sera
Precipitating U1 and U 2 Small Nuclear RNAs
T. Tojo, T. Ogasawara, Y. Okano, T. Mimori, and M. Homma
Keio University School of Medicine, Tokyo, Japan
Autoantibodies to U small nuclear ribonucleoproteins (UsnRNP) are known
to have close clinical associations in certain rheumatic diseases. Antigenic
epitopes of anti-U2RNP antibody have been shown to be present in A' (31 kD)
or B" (28.5 kD) polypeptides of U2 snRNP molecule from HeLa cells. However
due to the cross reactive epitopes present both in the B" of U2 RNP and the A
(33 kD) peptides U1 RNP, sera with anti-U2 RNP also immunoprecipitate U1
RNA. Because of this crossreactivity and the limited number of patients with the
sera, the exact clinical implication of the antibodies still remains unsatisfactory.
To get a better understanding of immunospecificities and clinical associations
of the antibodies in sera that immunoprecipitate both U1 and U2 snRNAs, pa-
tients with systemic rheumatic diseases were investigated. Sera from these patients
were screened for UsnRNAs by immunoprecipitation method using 32p-labelled
HeLa cell extracts. We found 10 sera that precipitated only U1 and U2 RNAs but
not U4, U 5 and U6. Immunospecificities of these sera could not be differentiated
from those containing only anti-U 1 RNP antibodies by conventional double im-
munodiffusion or passive hemagglutination tests. By immunoblotting analysis us-
ing substrates enriched for either U1 or U 2 RNP, all ten sera were shown to react
with both B" and A peptides indicating the presence of common antibodies to
U1/U2 RNP in these sera. Nine sera were also shown to react with 68 k peptides
of U1 RNP indicating the presence of antibodies to U1 RNP. This reactivity to
68 k peptides could be confirmed by enzyme-linked immunosorbent assay using
isolated peptides as the antigen.
The clinical characteristics of these patients were compaired with those of pa-
tients having anti-U 1 RNP or anti-U 1 U 2 U 4-6 RNP (Sm) antibodies. Incidence
of sclerotic skin changes confined to fingers or forearms and mild myopathy with
slightly increased serum levels of creatinine phosphokinase was significantly
higher than that in both groups of patients with anti-U 1 RNP or anti-U 1 U2
U4-6 RNP (Sm) antibodies.
The results confirmed the previously reported immunospecificity of anti-U 2
RNP antibody and indicate that patients with anti-U 1 /U 2 RNP antibodies may
be classified into an unique clinical subset in heterogeneous groups of patients
with overlapping features including those with mixed connective tissue disease.
99
Immunospecificity and Clinical Association of Autoantibodies in Sera
Precipitating U1 and U 2 Small Nuclear RNAs
T. Tojo, T. Ogasawara, Y. Okano, T. Mimori, and M. Homma
Keio University School of Medicine, Tokyo, Japan
Autoantibodies to U small nuclear ribonucleoproteins (UsnRNP) are known
to have close clinical associations in certain rheumatic diseases. Antigenic
epitopes of anti-U2RNP antibody have been shown to be present in A' (31 kD)
or B" (28.5 kD) polypeptides of U2 snRNP molecule from HeLa cells. However
due to the cross reactive epitopes present both in the B" of U2 RNP and the A
(33 kD) peptides U1 RNP, sera with anti-U2 RNP also immunoprecipitate U1
RNA. Because of this crossreactivity and the limited number of patients with the
sera, the exact clinical implication of the antibodies still remains unsatisfactory.
To get a better understanding of immunospecificities and clinical associations
of the antibodies in sera that immunoprecipitate both U1 and U2 snRNAs, pa-
tients with systemic rheumatic diseases were investigated. Sera from these patients
were screened for UsnRNAs by immunoprecipitation method using 32p-labelled
HeLa cell extracts. We found 10 sera that precipitated only U1 and U2 RNAs but
not U4, U 5 and U6. Immunospecificities of these sera could not be differentiated
from those containing only anti-U 1 RNP antibodies by conventional double im-
munodiffusion or passive hemagglutination tests. By immunoblotting analysis us-
ing substrates enriched for either U1 or U 2 RNP, all ten sera were shown to react
with both B" and A peptides indicating the presence of common antibodies to
U1/U2 RNP in these sera. Nine sera were also shown to react with 68 k peptides
of U1 RNP indicating the presence of antibodies to U1 RNP. This reactivity to
68 k peptides could be confirmed by enzyme-linked immunosorbent assay using
isolated peptides as the antigen.
The clinical characteristics of these patients were compaired with those of pa-
tients having anti-U 1 RNP or anti-U 1 U 2 U 4-6 RNP (Sm) antibodies. Incidence
of sclerotic skin changes confined to fingers or forearms and mild myopathy with
slightly increased serum levels of creatinine phosphokinase was significantly
higher than that in both groups of patients with anti-U 1 RNP or anti-U 1 U2
U4-6 RNP (Sm) antibodies.
The results confirmed the previously reported immunospecificity of anti-U 2
RNP antibody and indicate that patients with anti-U 1 /U 2 RNP antibodies may
be classified into an unique clinical subset in heterogeneous groups of patients
with overlapping features including those with mixed connective tissue disease.