Among the target antigens of antinuclear antibodies, more than 10 kinds of nuclear antigens such as Sm antigen, RNP, SS-A, SS-B, and Scl-70 can be extracted from the nucleus by isotonic saline, so they were collectively referred to as extractable nuclei in the past. Antigen (extractablenuclearantigen, ENA). The Sm antigen-antibody system is the first non-histone nucleoprotein antigen system discovered by Chen Yongming in 1966 in a patient with SLE. The main protein antigens in the Sm system are B, B', D, and E proteins with a molecular weight of 11 to 29 kD, in addition to A, A', B", C, F, G, and 68 kD, 150 kD, etc. These proteins and The guanosine-rich small nuclear RNAs (snRNAs), ie, UsnRNAs, form a complex. Currently, at least 13 UsnRNAs, ie, U1 to U13snRNAs, are found in mammals. Sm antigens are composed of U1, U2, U5, U4/U6 and the above proteins. It constitutes a small nuclear ribonucleoprotein (U1, U2, U5, U4/U6snRNP), which plays an important role in the transformation of heterogeneous nuclear RNA (hnRNA) into mature messenger RNA (mRNA). The hnRN of DNA transcription is outside the coding fragment. Exons and interrupted insertion of non-coding fragment introns. When hnRNA is transformed into mRNA, the RNA portion of U1, U2, U5, U4/U6RNP molecules is cleaved off non-coding sequences (introns) Re-linking the encoded RNA sequence (exon) plays an important role. After this splicing, mature mRNA is produced, enters the cytoplasm, and is translated into protein on the ribosome. It has been confirmed that anti-Sm antibody can enter living lymphocytes. May interfere with its function after binding to the target antigen, inhibiting cell proliferation, Secretion of cytokines (IFN-γ, IL-2, etc.) and induction of apoptosis.

Basic Information

Specialist classification: growth and development check classification: immunological examination

Applicable gender: whether men and women apply fasting: not fasting

Analysis results:

Below normal:

Normal value:

Above normal:

Normal human anti-Sm antibodies were negative.

A positive indication is abnormal.

Tips: There is no significant improvement in the positive rate of convection immunoelectrophoresis or agar two-way diffusion. Normal value

Normal human anti-Sm antibodies were negative.

Clinical significance

It is currently believed that anti-Sm antibodies, like anti-dsDNA, are highly specific for SLE, and anti-Sm can be positive regardless of active phase, so it can be used as a marker antibody for SLE. However, SML-positive patients account for only about 30% (20% to 30%) of SLE-positive patients, so SLE diagnosis cannot be ruled out when anti-Sm is negative. There is no consensus on the relationship between anti-Sm antibodies and clinical symptoms and disease outcomes.


The advantage of immunoblotting is that 7 peptide antibodies can be detected at the same time, but the positive rate is not significantly improved compared with convection immunoelectrophoresis or agar double diffusion method (mainly because the target antigen is thermally denatured, so that it exists on the surface of the molecule). The epitope has changed). Therefore, the corresponding polypeptide antibody is negative and does not rule out the presence of certain rheumatism.

Inspection process

Same as immunoblotting.

Not suitable for the crowd

There are no taboos.

Adverse reactions and risks

There are no related complications and hazards.