Natural killer activity and low-affinity E rosettes in acute leukemias.

Area of Science:

• Immunology
• Hematology
• Oncology

Background:

• Natural killer (NK) cells are crucial for innate immunity and cancer surveillance.
• Acute leukemia is a hematologic malignancy characterized by uncontrolled proliferation of immature white blood cells.
• Assessing immune function in leukemia patients during remission is important for understanding disease recurrence and treatment efficacy.

Purpose of the Study:

• To investigate natural killer (NK) cell activity in patients with acute leukemia in complete remission.
• To compare NK cell activity and membrane features in leukemia patients versus normal subjects.
• To explore the relationship between NK cell activity and the duration of complete remission.

Main Methods:

• Peripheral blood lymphocytes were isolated from 16 acute leukemia patients in complete remission and 19 healthy controls.
• NK cell activity was assessed using a short-term chromium release assay against the K562 target cell line.
• The number of cells with NK membrane features (low-affinity receptors for sheep red blood cells) was quantified.

Main Results:

• The majority of acute leukemia patients in remission exhibited significantly reduced NK cell activity against K562 target cells.
• The number of lymphocytes with NK membrane features was comparable between patients and normal subjects.
• Only two patients, those with the longest complete remission, showed good levels of NK activity.
• NK activity was normal in two individuals with preleukemic conditions.

Conclusions:

• NK cell cytotoxic function is generally impaired in acute leukemia patients even during complete remission.
• The persistence of NK membrane features suggests that the defect may lie in functional activation rather than cell numbers.
• Longer remission duration may be associated with better preserved NK cell activity, potentially indicating a role in maintaining remission.
• NK cell activity appears normal in preleukemic states, suggesting impairment occurs during or after leukemic transformation.