Cell mediated lympholysis; a modified technique using 111indium-oxine-labelled targets

Area of Science:

• Immunology
• Cellular Biology
• Radiochemistry

Background:

• The standard 51Cr isotope for cell-mediated lympholysis (CML) assays has limitations including low specific activity, poor incorporation, and high spontaneous release.
• These drawbacks restrict the duration of CML assays to 4-6 hours, potentially limiting sensitivity.

Purpose of the Study:

• To evaluate 111indium-oxine as a novel labeling agent for human lymphoblasts in CML assays.
• To assess the feasibility of extending CML assay duration and improving sensitivity using 111indium-oxine.

Main Methods:

• Human lymphoblasts were labeled with 111indium-oxine.
• Incorporation efficiency and spontaneous release rates were determined in the absence and presence of serum.
• The effector phase duration was extended to 18 hours, and cytotoxicity was measured at an effector to target ratio of 25:1.

Main Results:

• High incorporation (approx. 85%) of 111indium-oxine into lymphoblasts was achieved in serum-free conditions.
• Low spontaneous release (1.6-2%/h) allowed for an extended 18-hour effector phase.
• Extending the assay duration significantly increased cytotoxicity, with average specific release rising from 15% to 50% at a 25:1 ratio.

Conclusions:

• 111indium-oxine labeling offers improved sensitivity and allows for longer incubation periods in CML assays compared to 51Cr.
• This method enables the use of fewer effector and target cells, enhancing the efficiency of CML testing.