CCL22 and allergic disease: CCR4 is expressed by Th2 cells 5, 6, 7 with the number of CCR4+ T cells reported to be significantly upregulated in the peripheral blood and airways of patients with severe and moderate asthma, despite ongoing corticosteroid treatment.26 Combined with a substantial body of evidence detailing the production of both CCL17 and CCL22 in the allergic lung (reviewed by Solari and Pease 27), it is apparent that targeting CCR4 in allergic disease is attractive.