Abstract
Intra-thymic injection is a powerful tool for adoptive transfer of cells, cellular tag reagents for tracking recent thymic emigrants (RTEs), or other substances directly into the thymus. The traditional approach developed decades ago requires an invasive surgery to open the thoracic cavity and visualize the thymus. Subsequently, a technique was developed requiring only a small skin incision needed to identify the precise injection site. Nevertheless, both techniques require surgical intervention, and this can lead to elevated animal stress levels and pain which necessitates analgesic medication administration. Here we describe a less invasive technique allowing in situ visualization and transfer of cell suspensions or substances into the thymus via an ultrasound-guided intra-thymic injection approach.