1987 Chandran, et al: Anti-P in lupus Personal non-commercial use only. The Journal of Rheumatology Copyright © 2006. All rights reserved. Lack of Clinical Association with Antibodies to Ribosomal P Proteins in Indian Patients with Systemic Lupus Erythematosus VINOD CHANDRAN, SUNDEEP KUMAR UPADHYAYA, NIGIL HAROON, AMITAAGGARWAL, and RAMNATH MISRA ABSTRACT. Objective. We examined the prevalence and clinical association of the antiribosomal antibodies in our cohort of patients with systemic lupus erythematosus (SLE). Methods. IgG antiribosomal P protein (anti-P) antibodies were detected in 202 consecutive patients with SLE and 212 age and sex matched healthy subjects by an in-house ELISA, using the 22-mer C- terminal peptide. In 13 patients, IgG anti-P antibodies were also tested in paired cerebrospinal fluid (CSF) and sera samples. Clinical variables were compared in the antibody-positive and negative groups using appropriate statistical tests. Results. Of the 202 patients, 15 were male. Their median age was 30 years and the median disease dura- tion was 36 months. Thirty-one patients (15.35%) were positive for IgG anti-P antibodies, of which 24 were also positive by Western blot. No association with SLE Disease Activity Index, nervous system disease, nephritis, hepatitis, skin disease, arthritis, and juvenile onset disease could be demonstrated. Levels of IgG anti-P antibodies in CSF were 100-fold less compared to levels in serum, and correlated well with the latter (r = 0.86; p < 0.01). Conclusion. The prevalence of IgG anti-P antibodies is similar in Indian and Caucasian patients with SLE. No association with specific organ involvement or age at onset could be demonstrated. (J Rheumatol 2006;33:1987–9) Key Indexing Terms: CONNECTIVE TISSUE DISEASE AUTOANTIBODIES INDIA NEUROLOGICAL MANIFESTATIONS From the Department of Immunology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India. V. Chandran, DM, Senior Resident, Clinical Immunology; S.K. Upadhyaya, DM, Senior Resident, Clinical Immunology (currently Consultant Rheumatologist, Apollo Hospital, New Delhi, India); N. Haroon, MD, Senior Resident, Medicine; A. Aggarwal, DM, Associate Professor of Clinical Immunology; R. Misra, MD, Professor of Clinical Immunology. Address reprint requests to Prof. R. Misra, Department of Immunology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India 226 014. E-mail: rnmisra@sgpgi.ac.in Accepted for publication May 15, 2006. Antibodies to ribosomal P proteins (anti-P), directed against P 0 ,P 1 , and P 2 proteins located on the 60S subunit of eukary- otic ribosomes, occur specifically in systemic lupus erythe- matosus (SLE) 1 . A common epitope of 22 amino acid residues is located at the carboxy-terminal end of all the 3 P proteins 2 . The prevalence of these antibodies in SLE varies between 6% and 46% in various ethnic groups 3,4 . Clinical association with neuropsychiatric disease, especially psychosis 3,5,6 , nephri- tis 7,8 , hepatitis 7,9 , skin 10 , and age at onset of disease 11 is described in some but not in all studies 10,12 . We investigated the prevalence of these antibodies and its relation with clini- cal manifestations in our cohort of patients with lupus. MATERIALS AND METHODS All consecutive patients with SLE [American College of Rheumatology (ACR) 1982 criteria 13 ] attending our clinic between January 2000 and August 2002 were included in the study. Disease activity was measured at the time of sample collection using the SLE Disease Activity Index (SLEDAI). Cumulative clinical manifestations up to the time of assessment were includ- ed. Active neuropsychiatric lupus was diagnosed according to ACR guide- lines 14 . Nephritis was diagnosed if the patient had urinary sediment abnor- malities and proteinuria > 500 mg in 24 hours. Hepatitis was diagnosed if the levels of serum bilirubin and serum alanine and/or aspartate aminotransferas- es were abnormal after excluding drug and viral etiologies. Sera from 212 age and sex matched healthy individuals were collected as controls. Paired cere- brospinal fluid (CSF) and serum samples were collected from 13 patients with neuropsychiatric lupus during CSF examination. All samples were stored at –40°C until analysis. ELISA for IgG anti-P antibodies. ELISA was done using the C-terminal 22- mer peptide of ribosomal Pproteins, Lys-Lys-Glu-Glu-Lys-Lys-Glu-Glu-Ser- Glu-Glu-Glu-Asp-Glu-Asp-Met-Gly-Phe-Gly-Leu-Phe-Asp. A quantity of 50 μl/well of peptide (5 μg/ml) was coated and incubated at 37°C for 1 h, and then at 4°C overnight. The following morning, the plates were washed with phosphate buffered saline (PBS) and blocked with 200 μl PBS containing 3% bovine serum albumin (PBS-BSA) for 2 h at 37°C. Then 100 μl/well of 1:100 diluted test and positive control (1:400–1:25,600) sera in 0.1% PBS-BSA was added in duplicate and incubated 2 h at 37°C. Bound antibodies were devel- oped with rabbit anti-human IgG-horseradish peroxidase (Dako, Glostrup, Denmark) and OPD in substrate buffer and read at 492 nm with an ELISA reader (Tecan, Spectra, Salzburg, Austria). The value of the test sera was expressed as arbitrary units and read against the standard. Sera with values above mean + 5 SD (14.7 au/ml) of 212 healthy controls were taken as posi- www.jrheum.org Downloaded on December 24, 2021 from