Serum antibodies against the 70k polypeptides of the U1 ribonucleoprotein complex are associated with psychiatric syndromes in systemic lupus erythematosus: a retrospective study

Abstract

We assessed the association between serum autoantibodies against the 70-kDa polypeptide of the U1-ribonucleoprotein (RNP) complex (U1-70k) and the central nervous system (CNS) syndromes in systemic lupus erythematosus (SLE) patients. We studied 106 hospitalized patients with active SLE, comparing those with (n=32) and without (n=74) CNS syndromes. CNS syndromes were further classified into neurologic (n=21) and psychiatric (n=15) disorders. Immunoglobulin G (IgG) anti-U1-70k antibodies were measured by enzyme-linked immunosorbent assay (ELISA) using recombinant antigens. IgG antibodies against whole U1-RNP were measured using commercial ELISA kits. Although there was no significant difference in the levels of serum anti-U1-70k antibodies in SLE patients with or without CNS syndromes (p=0.83), the levels were significantly elevated in SLE patients compared with patients without psychiatric syndromes (p=0.030). In contrast, no significant difference was observed in the levels of serum anti-U1-RNP antibodies in SLE patients with or without psychiatric syndromes (p=0.555). These results indicate that serum anti-U1-70k antibodies are associated with psychiatric syndromes in SLE but that they are not associated with CNS syndromes as a whole or with neurologic syndromes. The anti-U1-70k antibodies might be involved in the pathological mechanisms of psychiatric syndromes in SLE.