CD45RO EXPRESSION ON PERIPHERAL LYMPHOCYTES AS A PROGNOSTIC MARKER FOR ADULT T-CELL LEUKEMIA

Adult T-cell leukemia (ATL) is an aggressive hematological malignancy etiologically linked to HTLV-I. The clinical subtype classification, a ge, performance status, serum calcium and LDH levels are major prognos tic factors of ATL, but these criteria and factors do not always corre late with prognosis. CD45 is expressed on cells of the hematopoietic s ystem, and plays a pivotal role in antigen-stimulated proliferation of T-lymphocytes. CD45RO is a very Light weight isoform of CD45 expresse d on activated T-cells. Recent studies have shown that peripheral lymp hocytes show two patterns of CD45RO expression in HTLV-I infected indi viduals which appears to correlate with their clinical outcome. The ac ute type ATL patients have pattern A with CD45RO(+) lymphocytes with i ntermediate expression (CD45ROint cells), and show a better prognosis than those who do not have any CD45ROint cells. Further studies demons trated that CD45ROint cells were not infected with HTLV-I, and as a re sult we suggest that CD45RO expression be considered a marker of host immunity in acute type ATL clinical course, in contrast to the levels of WBC or LDH which are regarded as tumor markers and indicators of tu mor mass.