Characterization of human null cells isolated from peripheral lymphocytes by a simultaneous double-rosetting...

Area of Science:

• Immunology
• Cell Biology

Background:

• Peripheral blood lymphocytes (PBL) comprise various immune cell types, including B and T lymphocytes.
• Characterizing distinct lymphocyte subsets is crucial for understanding immune responses and developing targeted therapies.

Purpose of the Study:

• To isolate and characterize human null cells from PBL.
• To investigate the functional properties and marker expression of these null cells.

Main Methods:

• Human null cells were isolated using differential centrifugation and Ficoll-Hypaque gradients.
• Lymphocytes were separated based on rosetting techniques with specific erythrocyte indicators for B and T cells.
• Flow cytometry and functional assays were employed to analyze cell markers and cytotoxic activity.

Main Results:

• Isolated null cells comprised approximately 90% of the lymphocytes and lacked detectable B-cell (surface immunoglobulin, Ia-like antigens) and T-cell (ShE receptors) markers.
• Null cells predominantly expressed receptors for IgG Fc fragment, C3 component, and monkey erythrocytes.
• These null cells demonstrated potent natural killer (NK) cell activity and antibody-dependent cellular cytotoxicity (ADCC), exceeding that of total PBL and T-enriched fractions.
• Null cells did not respond to phytohaemagglutinin (PHA) stimulation or participate in mixed lymphocyte reactions (MLR).

Conclusions:

• Human null cells represent a distinct lymphocyte population lacking conventional B and T cell markers.
• Null cells possess significant cytotoxic functions, including NK cell activity and ADCC.
• Their unresponsiveness to PHA and MLR suggests a specialized role in innate immunity rather than adaptive immune responses.