CD163, a novel receptor for TNF, was revealed in situ by proximity ligation assay

Cytokine therapy utilizes cytokines to enhance the immune system to fight diseases. These strategies rely on advanced knowledge, including the communication between cytokines and their receptors. <i>In situ,</i> cytokine-receptor interactions are typically analyzed by co-localization using immunolabeling. Our study compared co-localization using the Proximity Ligation Assay (PLA), a recently developed <i>in situ</i> protein-protein interaction technique. In an inflamed porcine lung model, we demonstrated the efficacy of PLA in detecting interactions between tumor necrosis factor (TNF) and its receptors TNFR1 and TNFR2. Additionally, the CD163 receptor was identified as a novel partner of TNF. Furthermore, the combination of immunolabeling and PLA offered additional insights, particularly, the internalization of TNF following its binding with CD163 in macrophages. Our work focused on <i>in situ</i> interactions of TNF with macrophages TNF receptors and suggested exciting perspectives for further understanding and application of cytokine-based therapies.