75Se-release: a short and long term assay system for cellular cytoxicity

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Cytotoxic assays are crucial for evaluating immune responses and drug efficacy.
• Accurate cell labeling is essential for reliable measurement of cell killing.
• Existing labels like 51Cr have limitations in sensitivity and stability.

Purpose of the Study:

• To evaluate 75Se-selenomethionine (75SeM) as a novel target cell label for cytotoxic assays.
• To compare the performance of 75SeM labeling with the traditional 51Cr labeling method.
• To assess the suitability of 75SeM for both short-term and long-term cytotoxic assays.

Main Methods:

• Activated cells were labeled with 75SeM in methionine-deficient medium.
• Cell viability, radioactivity uptake, and isotope release were measured over time.
• Cytotoxic reactions, including ADCC, were performed using labeled target cells.
• Comparison with 51Cr-labeled cells was conducted under identical conditions.

Main Results:

• 75SeM was efficiently incorporated into activated, metabolically active cells.
• 75SeM-labeled cells showed high radioactivity per cell and maintained viability for at least 72 hours.
• The assay demonstrated low baseline isotope release, enabling sensitive detection of cytotoxicity.
• 75SeM allowed for microscale assays with fewer target cells compared to 51Cr.
• Double gamma-labeling with 75Se and 51Cr enabled simultaneous monitoring of cellular interactions.

Conclusions:

• 75Se-selenomethionine is a superior label for cytotoxic assays due to its high uptake, stability, and sensitivity.
• The 75SeM assay is versatile, suitable for short and long-term studies, and adaptable to microscale formats.
• Dual labeling with 75Se and 51Cr offers enhanced capabilities for studying complex cellular interactions.