T-lymphocytes modulate the microvascular and inflammatory responses to intestinal ischemia-reperfusion

The overall objective of this study was to define the contribution of T-lymphocytes to the microvascular and inflammatory responses of the intestine to ischemia/reperfusion (I/R).

The superior mesenteric artery of wild-type (WT) and SCID mice was occluded for 45 minutes, followed by 30 minutes or 6 hours of reperfusion. Intravital fluorescence microscopy was used to monitor the extravasation of FITC-labeled albumin or the adhesion of carboxy-fluorescein diacetate succinimidyl ester (CFSE)-labeled T-lymphocytes in mucosal venules of the postischemic intestine. Tissue myeloperoxidase (MPO) was used to monitor neutrophil accumulation in the intestine of WT and SCID mice.

Although the number of adherent T-cells was not increased above baseline at 1 hour after reperfusion, significant T-cell adhesion (both CD4(+) and CD8(+)) was noted at 6 hours of reperfusion. The latter response was prevented by pretreatment with a blocking antibody directed against MAdCAM-1, but not ICAM-1 or VCAM-1. A significant increase in MAdCAM-1 expression was noted in both lymphoid (Peyer's patch) and nonlymphoid regions of the postischemic small bowel. The early (30 minutes after reperfusion) albumin extravasation elicited by gut I/R in WT mice was reduced in SCID mice. Reconstitution of SCID mice with T-lymphocytes restored the albumin leakage response to WT levels. The increased intestinal MPO caused by I/R (6 hours of reperfusion) in WT mice was attenuated in SCID mice; with reconstitution of SCID mice with T-cells the MPO response was restored.

These findings indicate that intestinal I/R is associated with the recruitment of CD4+ and CD8+ T-cells, which is mediated by endothelial MAdCAM-1. T-cells seem to modulate the recruitment of neutrophils that occurs hours after reperfusion as well as the increased albumin extravasation that occurs within minutes after reperfusion.