Correlation between effector lymphocytes in natural and antibody-mediated cytotoxicity

Area of Science:

• Immunology
• Cellular Biology
• Cytotoxicity

Background:

• Spontaneous cell-mediated cytotoxicity (SCMC) is a key immune function of lymphocytes.
• The precise mechanisms and effector cells involved in SCMC are not fully understood.
• Antibody involvement in SCMC has been suggested but requires further investigation.

Purpose of the Study:

• To elucidate the mechanisms of spontaneous cell-mediated cytotoxicity (SCMC).
• To determine the role of antibodies and Fc receptors in SCMC.
• To compare SCMC with antibody-dependent cell-mediated cytotoxicity (ADCC).

Main Methods:

• Human sera and anti-IgG (Fab')2 treatment were used to assess antibody involvement in SCMC.
• Trypsin treatment of effector cells evaluated the role of cell surface components.
• Target cell adherence (rosetting) and Ficoll gradient centrifugation were employed to isolate effector cells.
• SCMC and ADCC were measured before and after effector cell depletion.

Main Results:

• Human sera enhanced SCMC, while anti-IgG (Fab')2 treatment reduced it, indicating antibody involvement.
• Trypsin treatment significantly decreased cytotoxic potential, suggesting surface molecule importance.
• Serum-free conditions revealed a significant, inherent SCMC activity.
• Depletion of Fc receptor-bearing cells reduced both SCMC (78%) and ADCC (66%), suggesting shared effector cells.

Conclusions:

• SCMC is a complex activity involving both serum/surface-bound antibodies and intrinsic lymphocyte functions.
• A portion of SCMC activity is antibody-independent (sui generis).
• SCMC and ADCC likely involve the same lymphocyte populations, with differences attributed to effector cell numbers.