Scavenging of Hydrogen Peroxide — A New Mechanism of Action for d-Penicillamine in Rheumatoid Arthritis?

To the Editor: Although d-penicillamine has been used for many years in the treatment of rheumatoid arthritis, its mechanism of action still remains obscure. Recently, it has been shown that the addition of copper to d-penicillamine results in inhibition of in vitro T-lymphocyte proliferation, which can be antagonized by the addition of catalase. 1 The immunosuppressive action of copper-complexed d-penicillamine may therefore result from hydrogen peroxide production, which in turn leads to inhibition of cellular function or direct cytotoxicity. Employing an in vitro microplate assay system using hydrogen peroxide–dependent oxidation of phenol red, 2 we have confirmed that the addition of copper . . . No extract is available for articles shorter than 400 words.