How lung infection leads to gut injury

In 1979, John Bienenstock explored the origin of B cells in the mucosal tissues, including intestinal, respiratory and genital tract, and found that donor mice derived mesenteric lymph node B cells could be detected in most mucosal tissues of recipient mice, while peripheral lymph node B cells returned to their site of origin after adaptive transfer. Therefore, he presented a concept of “common mucosal immune system” and speculated that the mucosal immune system might be a system-wide “organ” in which the immune cells distributed throughout the body could interplay among different mucosal tissues [1]. The concept has been presented over 30 years, although some studies provided evidences to support it, there are still some questions need to be clarified. For example, what is the mechanism that regulates the immune cell migration among different mucosal tissues, and whether there are specific passages to connect different mucosal tissues and mediate immune cell migration [2]?