A comprehensive 26‐color immunophenotyping panel to study the role of the gut‐liver axis in chronic liver diseases

The gut‐liver axis includes the bidirectional communication between the gut and the liver, and thus covers signals from liver‐to‐gut and from gut‐to‐liver. Disruptions of the gut‐liver axis have been associated with the progression of chronic liver diseases, including alcohol‐related and metabolic dysfunction‐associated steatotic liver disease and cholangiopathies. Immune cells and their expression of pattern recognition receptors, activation markers or immune checkpoints might play an active role in the communication between gut and liver. Here, we present a 26‐color full spectrum flow cytometry panel for human cells to decipher the role of circulating immune cells in gut‐liver communication during the progression of chronic liver diseases in a non‐invasive manner, which has been optimized to be used on patient‐derived whole blood samples, the most abundantly available clinical material. Our panel focuses on changes in pattern recognition receptors, including toll‐like receptors (TLRs) or Dectin‐1, and also includes other immunomodulatory molecules such as bile acid receptors and checkpoint molecules. Moreover, this panel can be utilized to follow the progression of chronic liver diseases and could be used as a tool to evaluate the efficiency of therapeutic targets directed against microbial mediators or modulating immune cell activation.