An Immunohistochemical Analysis of Peripheral Blood Tissue Specimens from Leukemia Cells: Leukemic Cells of Adult T-cell Leukemia/Lymphoma Express p40Tax Protein of Human T-cell Lymphotropic Virus Type 1 When Entering Reproliferation

Abstract

Human T-cell lymphotropic virus type 1 (HTLV-1) proviral DNA p40Tax (Tax) protein plays an important role in adult T-cell leukemia/lymphoma (ATLL) oncogenesis, but it has yet to be determined whether or not ATLL leukemic cells express Tax. In a study designed to answer this question, we prepared peripheral blood tissue specimens (PBTS) from four acute and seven chronic ATLL cases and three B-cell chronic lymphocyte leukemia (B-CLL) cases, and examined their immunological phenotype and Ki67 labeling index (Ki67LI) by means of antigen-retrieval immunohistochemistry. In three of the chronic ATLL cases, the difference in Ki67LI between leukemic cells that underwent either 3 hr, or more than 6 hr of sedimentation and coagulation while preparing PBTS suggested that the Ki67LI in PBTS represents reproliferating cells. Tax expression was examined by means of the ImmunoMax method. In two acute and three chronic type ATLL cases, leukemic cells expressed Tax in parallel with the Ki67LI, suggesting that Tax expression was related to reproliferation in PBTS. Leukemic cells in one case each of acute and chronic type ATLL did not express Tax. In one case of acute ATLL after chemotherapy, some cells expressed Tax among the other cells. These results indicate that ATLL leukemic cells are able to express an extremely small amount of Tax during reproliferation.