NEW YORK (Reuters Health) – Genomic profiling of peripheral blood cells allows assignment of rheumatoid arthritis patients to different subtypes, according to findings reported by investigators in the Netherlands.

Dr. C. L. Verweij from VU University Medical Center, Amsterdam, and colleagues conducted large-scale expression profiling by cDNA microarrays on peripheral blood from 35 rheumatoid arthritis patients and 15 healthy individuals in an effort to identify profiles that may distinguish rheumatoid arthritis subtypes.

Two hundred fifty-nine genes were upregulated and 318 genes were downregulated in patients with rheumatoid arthritis compared with healthy controls, the authors report.

Among the genes upregulated in the patients was a prominent cluster of interferon-inducible genes, as well as several inflammatory mediators, members of the antioxidant metallothionein family, and the anti-inflammatory IL1 receptor antagonist.

Several downregulated genes were involved in cytotoxic functions, and many downregulated genes had unknown function.

Twenty of the 35 rheumatoid arthritis patients showed a high expression level of genes comprising a type 1 interferon signature; these patients showed upregulation of an additional 10 biological processes not upregulated in patients with low expression of the interferon signature genes.

"Overall, these analyses indicate that, within the whole group of patients, the high-expression interferon group is more distinct from controls than the low-expression interferon group," the investigators write in the August issue of the Annals of the Rheumatic Diseases.

"The interferon type 1 signature defines a subgroup of patients with rheumatoid arthritis, with a distinct biomolecular phenotype, characterized by increased activity of the innate defense system, coagulation and complement cascades, and fatty acid metabolism," the researchers conclude.

Ann Rheum Dis 2007;66:1008-1014.

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