In this article, we will focus upon the chemokine CCR4 and its ligands CCL17 and CCL22, which are postulated to play key roles in the pathogenesis of allergic asthma (Pease and Horuk, 2014), atopic dermatitis (Yamanaka and Mizutani, 2011) and a variety of cancers, including breast cancer (Li et al., 2012), gastric cancer (Yang et al., 2011) renal cell cancer (Liu et al., 2014) and lymphoma (Ishida and Ueda, 2011). The gene discussed is CCR4; the disease is lymphoma.