WesternBlots - ImmunoBlots                             


ANA Line Blot

Table of detectable auto-antibodies

Type of Antibody

Molecular weight (kD) of the antigen

Specificity of the antigens




Double stranded DNA

Specific marker for Systemic Lupus Erythematosus (SLE)



Sm consists of three proteins: B`(29 kD), B (28 kD) and D (19 kD), which share some epitopes


anti-U1 -snRNP 68/70



The antigenic structures are specific proteins of the snRNP called "small nuclear ribonucleoprotein complex". This complex is involved in various molecular processes, that take place in the nucleus. It contains proteins with molecular weights of about 70, 33 (protein A) and 22kD (protein C). In total six snRNP particles (U1 to U6) can be distinguished. These particles are complexes consisting of messenger- RNA (mRNA) and proteins. The main proteins of the particles U1, U2, U5 and U4/U6 contain the protein units B', B, D, E, F and G. The U1-snRNP 70 additionally contains the proteins A and C. All RNP particles are involved in the splicing of mRNA precursors. 

The occurrence of isolated anti-snRNP antibodies in the absence of anti-Sm is a pathognomic marker for mixed connective tissue diseases (MCTD) and shows a clinical sensitivity of 95-100%.

Bands at 33 kD may occur in parallel with the 70 kD- or the Sm-bands. Acc. to the literature (2) this band is indicative for the SLE and nephritis, existing or developping.

In combination with the 70kD RNP they are indicative for the SLE or MCTD.






anti-rib. RNP


These antibodies are directed against three subunit ribosomal phospho-proteins, called PO(38kD), P1(19kD) and P2(17kD).

They occur in approx. 12% of patients with SLE. Clinically, anti-ribosomal RNP antibodies are associated with lupus psychosis.

anti-Ro/SS-A1 -


Antibodies to Ro-antigens are indicative for the SLE or Sjögren`s Syndrome.

These auto-antibodies are directed against proteins of RNA-protein particles located in the nucleus. They may also be present in the cytoplasma. Antibodies to SS-A bind to a particular antigen that consists of two proteins with molecular weights of 60 and 52 kD, respectively, and small RNA particles of 80 to 112 nucleotides.






SSB is a nucleus-based particular antigen. It consists of a 52 kD phosphoprotein, which is associated with Polymerase III transcripts. In addition to human RNA, the protein may also bind to virus-encoded RNA. In general, the SS-B bands appear - with very few exceptions- only in combinaion with the Ro 52 kD-band.

Anti-SS-B antibodies can be demonstrated in 45% of SLE patients and in 90 % of patients with Sjögren´s Syndrome.

Clinically, these antibodies are indicative for SLE or Sjögren´s Syndrome with existing Sicca symptoms.

anti-Scl-70 - DNA

Topoisomerase I


Highly specific marker for progressive systemic scleroderma (PSS).

Occasionally, Scl 70 antibodies are detected in patients with circumscript or linear scleroderma. Diagnostic sensitivity of Scl 70 determination in progressive scleroderma is more than 70 % at a diagnostic specificity of about 100 %.




Pm-Scl is a complex consisting of 10 nucleolar antigens with an overall molecular weight of approx. 120 kD

Nearly in complete association with the disease of polymyositis and dermatomyositis.

Anti-Pm-Scl is a very rare, but highly specific marker for the scleroderma-polymyositis overlap syndrome.




The centromere is a special domain of eucaryontic DNA and adhesion point of the mitotic spindle fibres. Antibodies are directed against specific DNA associated proteins (CENP-A, -B and -C), most frequently against the CENP-B antigen.

Clinically ACA are relevant for patients with CREST syndrome and less frequent with scleroderma.




Jo-1 antibodies are highly specific markers for dermatomyositis or polymyostis.




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