Arthritis Research & Therapy (May 2007)

Association of cerebrospinal fluid anti-ribosomal P protein antibodies with diffuse psychiatric/neuropsychological syndromes in systemic lupus erythematosus

We explored the relationship of antibodies to the whole ribosomal P proteins (P0, P1, P2) in cerebrospinal fluid (CSF) with diffuse psychiatric/neuropsychological syndromes in systemic lupus erythematosus (SLE). CSF were obtained from 71 SLE patients (52 patients with diffuse psychiatric/neuropsychological syndromes [diffuse NP-SLE] and 19 patients with neurologic syndromes or peripheral neuropathy [focal NP-SLE]) as well as from 24 patients with non-inflammatory neurological disease. IgG antibodies to the C-terminal 22 amino acids ribosomal P synthetic peptide (anti-PC22) and those to purified bovine ribosomal P proteins (P0, P1, P2) (anti-whole P) were determined by enzyme-linked immunosorbent assay, using affinity purified IgG anti-PC22 as standard. The concentrations of antibodies to epitopes other than the C-terminal 22 amino acids of ribosomal P proteins were calculated by subtracting anti-PC22 from anti-whole P (anti-PEX.C22). CSF anti-whole P were significantly elevated in diffuse NP-SLE compared with focal NP-SLE or control patients. By contrast, there were no significant differences in CSF anti-PC22 levels among the 3 groups. Of note, CSF anti-PEX.C22 were significantly elevated in diffuse NP-SLE compared with the other 2 groups. CSF anti-PEX.C22 were not significantly correlated with CSF anti-PC22, but with CSF antibodies against the recombinant ribosomal P0 protein lacking the C-terminal 22 amino acids (C22-depleted rP0). Moreover, CSF anti-PEX.C22 or CSF anti- C22-depleted rP0, but not CSF anti-PC22, were significantly correlated with CSF anti-neuronal cell antibodies (anti-N). These results indicate that CSF IgG antibodies to the epitopes other than the C-terminal 22 amino acids of ribosomal P proteins, which might contain one of the major targets of CSF anti-N, are associated with the development of diffuse NP-SLE.