Adult T-cell leukemia/lymphoma(ATL), an entity originally proposed by Uchiyama et al., is an important malignant lymphoproliferative disorder closely associated with human T-cell leukemia virus type 1(HTLV-1), and frequently involves the skin. ATL has been classified into four clinical subtypes, smoldering, chronic, lymphoma, and acute, according to their clinical features, and the prognosis of ATL usually depends upon the subtype. The neoplastic T cells show an activated helper T-Cell lineage, that is, CD3, CD4, CD5, CD25, CD71 and HLA-DR positivity. However, some phenotypic discrepancy has been found between the neoplastic cells in the peripheral blood, lymph nodes and skin of patients with ATL with respect to CD45R isoform and adhesion molecules. That is, expression of CD45RA on the neoplastic cells is high in peripheral blood and low in the skin. On the other hand, expression of CD45RO, VLA4, LFA-1, ICAM-1 and CD29 on the neoplastic cells is low in the peripheral blood and high in
the skin. That is, there is a difference in expression of the CD45R isoform and adhesion molecules on ATL neoplastic cells according to their tissue distribution.
A phenotypic discrepancy has been found between neoplastic cells in the peripheral blood and those in the skin of patients with ATL.The MTY6-10 cell line was established from neoplastic cells in the peripheral blood of a patient with acute-type ATL, and showed a phenotype similar to that of the original peripheral blood neoplastic cells, i.e., CD45RA, L-selectin high, VLA4 low and CD45RO negative. The MTY6-10 cells were then cultured with endothelial cells, fibroblasts, keratinocytes or cytokines, and their surface phenotype was re-examined. Expression of CD45RA and L-selectin was decreased by co-culture with endothelial cells, fibroblasts or keratinocytes, or with IL-2 or IL-6. On the other hand, expression of CD45RO and VLA4 on the MTY6-10 cells was increased by co-culture with endothelial cells or keratinocytes, or with IL-1 or IFN-gamma. That is, the surface phenotype of the MTY6-10 cells showed a tendency for conversion from that of peripheral blood neoplastic cells to that of neoplastic cells in the skin upon co-culture with endothelial cells, keratinocytes, IL-1, IL-2, INF-gamma or IL-6. Less