Indium-111 labelled lymphocytes: isotope distribution and cell division

Area of Science:

• Immunology
• Nuclear Medicine
• Cell Biology

Background:

• Lymphocyte proliferation in vivo necessitates understanding radionuclide fate after labeling.
• Indium-111 (111In) is used for lymphocyte labeling, but its intracellular behavior requires investigation.

Purpose of the Study:

• To determine the distribution and fate of 111In in lymphocytes undergoing proliferation in vitro.
• To assess the impact of 111In labeling on lymphocyte metabolic activity and cell division.

Main Methods:

• Mixed lymphocyte reaction (MLR) was used to stimulate 111In-labeled rat lymphocytes (L10, L12.4 CD4+ T cells).
• 111In distribution between cells and supernatant was measured daily.
• Cell proliferation was assessed by cell counting.
• Metabolic activity was evaluated using fluorine-18 fluorodeoxyglucose ([18F]FDG) uptake.

Main Results:

• 111In-labeled lymphocytes exhibited reduced proliferation initially but increased later.
• Approximately 70% of 111In was found in the supernatant between 24-72 hours, primarily from viable cells.
• Viable cells initially retained more 111In, but this reversed as cells died, indicating active elimination.
• [18F]FDG uptake was higher in labeled cells at 24 hours, coinciding with reduced cell numbers.

Conclusions:

• Lymphocytes actively eliminate 111In, diverting energy from cell division and increasing cell death.
• As lymphocytes deplete 111In, proliferation capacity recovers and death risk decreases.
• Findings suggest that viable 111In-labeled lymphocytes will either die or eliminate the label, impacting scintigraphy interpretation.