Infections in patients with rheumatoid arthritis receiving anti-cytokine therapy: biological mechanisms and clinical aspects

Different animal studies show that several proinflammatory cytokines are essential for natural resistance to specific infections, particularly versus intracellular organisms. However, uncontrolled overproduction of some proinflammatory cytokines, in diseases such as rheumatoid arthritis, can be just as dangerous to the host as the absence of the same cytokines. Reduction in the production and/or activities of proinflammatory cytokines in rheumatoid arthritis remains a therapeutic objective for many patients. The tumour necrosis factor-alpha (TNF-α) blockers infliximab, etanercept and adalimumab and the recombinant interleukin 1 (IL-1) receptor antagonist anakinra are effective in patients with active rheumatoid arthritis. However, there is a growing body of clinical evidence that neutralization of TNF-α is associated with an increased risk of opportunistic infections, including mycobacterial diseases. Blockade of IL-1 activity with the IL-1 receptor antagonist (IL-1Ra) appears, at present, to be relatively safe. Postmarketing experience and pharmacovigilance programs are necessary to determine the overall safety profile of the new agents. At this time, treating physicians must weigh carefully the benefits of biologics against their safety, particularly in patients at risk of infection.