Tongue as a first-line immune organ?

The tongue is an organ strategically situated at the beginning of the gastrointestinal(Gl)system,yet it has been remarkably understudied.Not only there is no separate subspecialty dedicated to the tongue,it is even excluded from 27 human organs/tissues thoroughly archived in the NCBI gene expression database.Almost none of my physician colleagues in Western medicine have paid attention to it,except a few who study tongue cancer.The tongue is typically described as a muscular organ important for taste,mastication,speech and sensation.Other than its development,anatomy/gross structural analyses and taste function(for recent reviews,see Roper and Chaudhari,2017),the human tongue is poorly studied in Western medicine,in particular,in terms of its roles in systemic diseases.In traditional Chinese medicine(TCM),however,the tongue holds a special place.Assessing the“tongue coating”,"tongue body”and morphological features is one of the most critical skills that TCM doctors have relied on for disease diagnoses for thousands of years before the advent of Western Medicine.