CTACK/CCL27 is a member of the b or CC family of chemokines. It is found on human chromosome 9p13 and on murine chromosome 4. CCL27 is distinct from other chemokines in several ways: (1) its gene is located on the opposite reading frame overlapping the gene encoding the a chain of the interleukin 11 receptor (Baird et aL, 1999; Ishikawa-Mochizuki et al, 1999) and (2) it is specifically expressed in skin by keratinocytes (Morales et al, 1999). although alternatively spliced forms are also expressed in testis, heart, and liver (Hromas et al, 1999). CCL27 chemo-attracts CLA+ memory T cells. The CCL27 receptor is CCR10 (formerly known as GPR2) (Homey et al, 2000; Jarmin et al, 2000).