Mast cells are a native composer of connective tissue of the skin dermis and intestinal and respiratory mucosa. Independent lines of accumulated evidence indicate the existence of an intensive bidirectional crosstalk between mast cells and sensory nerves and suggest that mast cells and sensory nerves may be viewed as a functional unit, which could be of crucial importance in neuroimmunological pathways. Mast cells appear to have a property of influencing smooth muscle function via not only such nerve-mast cell effects, but also direct pathways. In bronchial asthma, mast cells infiltrate the airway smooth muscle layer, and interact directly with smooth muscle cells, suggesting pathogenic roles for mast cells in airway obstruction. Current studies on mast cell biology identified a novel adhesion molecule of mast cells, namely cell adhesion molecule-1, CADM1. This molecule is unique, because it serves as not only simple glue but also appears to promote functional communication between nerve and mast cells and between smooth muscle and mast cells.