ANTIBODIES TO RIBOSOMAL-P ANTIGENS

CLINICAL UTILITY:

The ribosomal-P antigen ("P" for the phosphoprotein constituents), is an epitope on the carboxyl-terminal 22-amino acid sequence common to the P0, P1, and P2 phosphoproteins associated with the large 60 S ribosomal subunit.

Ribosomal autoantibodies have been associated with Systemic Lupus Erythematosus (SLE), and are rarely seen in other conditions. It is occasionally found in "ANA negative" SLE patients. The antibody has been reported in 10-20% of unselected SLE sera, but the frequency varies with race. A 1993 report found the following frequency in various SLE populations: 38% - Malaysian Chinese, 13% - English, 20% - Afro-Caribbean. Reports have also linked the antibody with the active phase of lupus psychosis. However, there are still many discrepancies in the literature regarding the clinical associations of anti-ribosomal P antibodies in SLE.

Other methods of determining positive anti ribosomal antibody activity are immunofluorescence (positive chief cells on stomach tissue), or by Ouchterlony/ CIE. It is possible for the ELISA assay to show a negative result, while the IFA and/or Ouchterlony/CIE exhibit positive results. For example, one study has demonstrated anti ribosomal sera that binds to a small fragment of the 28S ribosomal subunit with no correlation in binding to the P0, P1, or P2 proteins. This could be one cause for any discrepancies noted between the results from IF, Ouchterlony, and ELISA.

METHOD DESCRIPTION:

Antibodies to Ribosomal-P Antigens are measured colorimetrically using a solid phase immunoenzymatic assay (“sandwich” technique).

REFERENCE RANGE:

Negative <20 Units; Weak Positive 20-39 Units; Moderate Positive 40-80 Units; Strong Positive >80 Units

SPECIMEN REQUIREMENTS:

The assay requires 1.0 ml of serum (minimum of 0.5 ml) collected in a red top tube and separated from the cells as soon as possible.