WesternBlots - ImmunoBlots                             


Rheumatoid Arthritis ImmunoBlot


Table of detectable auto-antibodies

Type of Antibody  

Molecular Weight, (kD)

Specificity of the antigens


55 kD *

* The 50 kD antigen is a degradation product of the 55 kD

The specificity of anti-Sa antibodies for Rheumatoid Arthritis was 98.9%, the positive predictive value was 96.7%, while its negative predictive value was 69.8%.

Anti-Sa antibodies occurred independently from rheumatoid factor (RF).

Testing of anti-Sa plus HLA class II DRB alleles (DRB1*01 and DRB1*04 subtypes) was the best combination of immunologic markers for the diagnosis of destructive adult RA.

anti- SS-A

60 kD,

52 kD

Demonstration of only 60kD SS-A antibodies suggest SLE, whereas 60kD plus 52kD SS-A antibodies are indicative of SLE or Sjögren's syndrome.


45 kD

SS-B antibodies usually - with rare exceptions - appear in combination with SS-A 52kD antibodies. SS-B antibodies are present in 45% of sera from SLE patients and in 90% of those from patients with Sjögren's syndrome.

not defined RA-associated antigen

~43 kD

In addition to the rheumatoid arthritis specific Sa-55 and Sa-50kD antigen bands a further not yet defined antigen band with a MW of ~43kD, only reacting with sera from patients with RA could be observed (Personal findings). Its relevance still has to be evaluated.




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