Complications and adverse reactions in the use of newer biologic agents.

New developments in genetic engineering and biotechnology have allowed the creation of bioengineered molecules that target specific steps in the pathogenesis of several immune-mediated disorders, including Crohn's disease, rheumatoid arthritis, psoriasis and psoriatic arthritis, ankylosing spondylitis, pemphigus, and B-cell lymphoma. These drugs work by eliminating pathogenic T cells (alefacept), blocking T-cell activation and/or inhibiting the trafficking of T cells (efalizumab), changing the immune profile from Th1 to Th2, blocking cytokines (eg, tumor necrosis factor alpha antagonists including etanercept, infliximab and adalimumab, or interleukin-1-receptor antagonists [anakinra]), or eliminating pathogenic B cells (rituximab). This article reviews the complications and adverse reactions associated with these medications.