Intercellular communication of immune cells is critical to elicit efficient 
inflammatory responses. In intestinal mucosa, imbalance in pro-inflammatory and 
anti-inflammatory mediators, especially cytokines and chemokines, characterizes 
the underlying immune mechanisms of inflammatory bowel disease. Exosomes, small 
membrane vesicles secreted into the extracellular environment, are emerging as 
another important intercellular messenger in immune responses. A major recent 
breakthrough in this field unveils the capacity of exosomes to mediate the 
functional transfer of genetic materials (mRNAs and miRNAs) between immune 
cells. RAB27A and RAB27B are two small GTPases involved in exosome secretion. 
With respect to intestinal mucosal immunity, increased number of RAB27A-positive 
immune cells and RAB27B-positive immune cells are demonstrated in the colonic 
mucosa of patients with active ulcerative colitis as compared with that of 
healthy controls. This indicates the important role of exosome-mediated immune 
responses in the pathogenesis of inflammatory bowel disease. Here, we will 
discuss the immune properties of exosomes and recent advances in their function 
with a special focus on intestinal mucosal immunity.