Single-cell assessment of iron content in primary human T cells using laser ablation inductively coupled plasma mass spectrometry

Transition metals, such as iron, support vital metabolic and signaling functions in immune cells. Cellular iron concentrations are tightly controlled. In T cells, both iron deficiency and iron overload have been linked to immune dysfunction. Homeostatic iron concentrations in T cells, and changes that occur during T cell activation, remain poorly understood due to difficulty of accurately measuring iron content in single cells, especially in small cells. Here, we describe the use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to accurately quantify the total amount of endogenous iron in individual primary human T cells. Our technique allows for targeted selection of single cells and reproducible quantification of iron at femtogram level. Our findings reveal that iron levels in resting T cells were similar across human donors. In contrast, T cell activation leads to diverse patterns between individual cells and donors, indicating specialized needs during differentiation.