Microcirculation (Second Edition): Chapter 14 - Gastrointestinal and Liver Microcirculations: Roles in Inflammation and Immunity

This chapter focuses on the role of the microvasculature in regulating the recruitment of leukocytes into the gastrointestinal (GI) tract and liver. The contributions of the GI and liver microcirculations to the assimilation of a meal, and other relationships between organ function and these vascular beds have also been discussed. An exciting and robust area of investigation related to GI and liver pathology is inflammation. There is a large body of evidence that implicates the microcirculation as a rate-determining component of the inflammatory cell recruitment and activation that occurs during inflammation of the GI tract and liver. Inflammatory diseases of the GI tract and liver are however characterized by a pronounced and persistent recruitment of inflammatory cells into these tissues, which, coupled with dysregulated activation of the infiltrating cells, ultimately results in tissue injury and organ dysfunction. Functional blood and lymph microcirculations in the intestine are essential for immune defense by controlling immune cell trafficking. Key elements of the trafficking of lymphoid cells through the intestine are summarized. Various types of leukocytes appear to contribute to the pathology of many different liver diseases. Depletion of leukocytes results in reduced injury in many of these disease states, however, it is worth noting that in some situations despite the accumulation of leukocytes, they may not be involved in injury. The leukocyte recruitment cascade as it pertains to the liver is summarized and the important and often controversial aspects of this work are highlighted.