Defective interleukin-2 induction of lymphokine-activated killer (LAK) activity in peripheral blood T lymphocytes of patients with monoclonal gammopathies

The recombinant interleukin-2 (rIL-2) generation of lymphokine-activated killer (LAK) cells was investigated in peripheral blood T lymphocytes (PBT) of 16 patients with monoclonal gammopathy of undetermined significance (MGUS) and 32 patients with multiple myeloma (MM). LAK activity was significantly decreased in MM, but not in MGUS patients, and was partially recovered in MM in the remission phase. This finding was unexpected, because CD8⁺ CD11b⁺ cells, which contain LAK precursors, are significantly increased in MM. LAK activity was investigated in purified CD8⁺CD11b⁺ lymphocytes to discriminate between an intrinsic defect or a defective regulation by other T cell subsets. These cells were intrinsically unable to generate LAK activity fully following rIL-2 stimulation. MM showed the more pronounced LAK deficiency, while MGUS patients showed intermediate values. Phenotyping revealed significantly increased proportions of Leu7⁺ and HLA-DR⁺ cells in MM patients. These data reveal another dysregulation of T cell effector functions in patients with monoclonal gammopathies and offer further evidence of the impairment of their cell-mediated immunity.