ribosomal-protein-l7-l12 and Autoimmune-Diseases

Autoantibodies to the 20-kDa ribosomal proteins (L12/S10) are not well studied, especially in juveniles with systemic lupus erythematosus (SLE). Randomly selected sera from American juveniles and adults with SLE were screened for antibodies to either 20-kDa protein and P proteins and then assayed for anti-L12 and anti-S10 by immunoblot assays. In a pilot study of patients with anti-P (Cohort 1), IgG antibodies to either 20-kDa protein and, specifically, to L12 were observed in 72 and 42% of juveniles and adults, respectively. IgG antibodies to S10 were detected less frequently. In Cohort 2 patients who were chosen irrespective of autoantibody status, twice as many juveniles as adults had IgG antibodies to either 20-kDa protein. Prevalences of IgG anti-L12 and IgG anti-S10 antibodies in the juveniles were 28 and 16% and in the adults were 13 and 12%, respectively. Anti-L12 were strongly but not invariably associated with anti-P, and usually arose temporally to these antibodies. Anti-S10 activity was due to anti-Sm antibodies. We conclude that IgG anti-L12 are more prevalent in SLE than previously reported, and are responsible for the majority of activity toward the 20-kDa ribosomal proteins, especially in juveniles.

Topics: Adolescent; Adult; Aged; Animals; Antibodies, Antinuclear; Autoantibodies; Autoantigens; Autoimmune Diseases; Child; Child, Preschool; Cohort Studies; DNA; Female; Humans; Immunoglobulin G; Lupus Erythematosus, Systemic; Male; Middle Aged; Pilot Projects; Rabbits; Rats; Ribonucleoproteins, Small Nuclear; Ribosomal Proteins; Ribosomes; snRNP Core Proteins

Site-specific anti-RNA antibodies were sought in 120 sera of patients with autoimmune diseases by ribonuclease-protection assay using six fragments covering 28S ribosomal RNA (rRNA) as antigens. Fifteen of 90 sera from patients with systemic lupus erythematosus (SLE), but none of 30 sera of the other autoimmune diseases, provided a 60 nucleotide fragment within a region termed the 'GTPase domain' of 28S rRNA. These sera had potency to precipitate 0.42-69.3 nmol of the RNA domain per ml serum, which was higher than 15 control sera of healthy donors. No other specific antigenic site was detected in 28S rRNA under conditions used. All of the 15 sera having this anti-RNA antibody showed reactivity to ribosomal P proteins (anti-P), and two of them contained an additional antibody to ribosomal protein L12. These results suggested a strong association of the production of these three antibodies. Since P and L12 proteins form a stable complex with the GTPase domain, this serological association may result from an immune response to epitopes clustered on a single RNA-protein complex domain in ribosomes.

Topics: Autoantibodies; Autoimmune Diseases; Base Sequence; Humans; Lupus Erythematosus, Systemic; Molecular Sequence Data; Protozoan Proteins; Radioimmunoassay; Ribonucleases; Ribosomal Proteins; RNA, Ribosomal, 28S