T-helper phenotype chronic lymphocytic leukaemia and "adult T-cell leukaemia" in Italy. Endemic HTLV-I-related T-cell leukaemias in southern Europe.

Sixteen Italian patients with chronic T-cell lymphocytic leukaemia (T-CLL) and leukaemic T-helper phenotype lymphocytes (Thp-CLL) were investigated for serum antibodies against human T-cell leukaemia virus I (HTLV-I) or its integrated DNA sequences. Common features of this series of patients were an aggressive clinical course with poor response to treatment, high white blood-cell count, bone-marrow infiltration, splenomegaly, and chromosome abnormalities. Three patients had skin infiltration and one had hypercalcaemia. Immunological analysis showed a Thp (OKT4+) in all cases, and a heterogeneity, within the OKT4 population, of phenotypes and functional activities. Three patients had either HTLV-I integrated DNA sequences or anti-HTLV-I serum antibodies, or both. These patients had not received any blood transfusions, denied intimate contact with foreigners, and had always lived in small towns of central or southern Italy. Clinical and immunological findings in this series of patients suggest that both HTLV-I related and unrelated cases of Thp-CLL should be regarded as one disease arising from the same subpopulation of mature T-lymphocytes.