Distinct phenotype of leukemic T cells with various tissue tropisms.

There is an emerging concept, the validity of which remains to be proven, that preferential expression of selective adhesion molecules on particular T cell subsets may result in tissue-specific migration. L-selectin, cutaneous lymphocyte-associated Ag (CLA), and integrin alpha4beta7 are proposed to be involved in selective migration of T cell subsets into peripheral lymph nodes, skin, and gastrointestinal mucosa, respectively. Adult T cell leukemia (ATL) is associated with lymphoid infiltration of tissues and secondary lymphoid organs. To clarify the role of these putative homing molecules in vivo, we assessed their expression on circulating ATL cells from patients with lymph node, skin, and gut involvement. L-selectin expression was significantly higher on peripheral ATL cells in patients with lymphadenopathy than in patients without it. CLA was highly expressed on peripheral ATL cells compared with normal T cells: its expression was also significantly higher on peripheral ATL cells from patients with skin involvement compared with cells from patients without it. beta7 was particularly highly expressed on peripheral ATL cells from patients with gastrointestinal involvement. In summary, the differential expression of beta7 and beta1 on peripheral ATL cells correlates with the presence of gastrointestinal involvement. Similarly, the presence of skin involvement is associated with the expression of CLA(high)beta7low on peripheral ATL cells. These results, which are consistent with the molecules CLA and alpha4beta7 mediating preferential T cell migration to the skin and gastrointestinal mucosa, respectively, may allow for a refinement of the classification of lymphoid neoplasms on the basis of differential expression of homing molecules.