Normal helper T-cell function in hairy-cell leukaemia.

The function of peripheral blood T-lymphocytes was tested in a series of untreated patients with hairy-cell leukaemia (HCL). The in vitro T-colony forming capacity fell within the normal range in 20 of the 22 cases studied. No difference in colony growth was found between splenectomized and non splenectomized patients. The ability to induce differentiation of normal B-lymphocytes into antibody producing plasma cells, in a pokeweed mitogen (PWM) stimulated system, was similar to that of normal T-cells in all 6 cases studied. Both the T-colony growth and the helper capacity were unrelated to the distribution of T-lymphocyte subsets defined by monoclonal antibodies, despite an increase in OKT8+ cells (suppressor/cytotoxic phenotype) and a decrease in OKT4+ cells (helper/inducer phenotype) in 44% of the patients. The significance of these findings is discussed in relation to T-cell abnormalities previously described in other B-cell leukaemias, chiefly chronic lymphocytic leukaemia (B-CLL). The preserved T-cell function in HCL correlates well with the normal humoral immunity found in this disease.