Gut ischemia-reperfusion affects gut mucosal immunity: A possible mechanism for infectious complications after severe surgical insults

OBJECTIVE:To examine influences of gut ischemia/reperfusion (I/R) on gut-associated lymphoid tissue (GALT) mass and function. DESIGN:Prospective, randomized controlled study. SETTING:Research laboratory. SUBJECTS:Male Institute of Cancer Research mice. INTERVENTIONS:Ninety mice were randomized to three groupsI/R (60-min gut ischemia), sham (laparotomy only), and control (no operation). On days 1, 2, 4, 7, and 10, mice were killed to harvest lymphocytes from Peyer patches, the intraepithelial space, and the lamina propria (LP) of the small intestine. Respiratory tract and small intestinal washings were also obtained. MEASUREMENTS AND MAIN RESULTS:Gut I/R significantly reduced lymphocyte numbers in Peyer patches, the intraepithelial space, and the LP. The reduction was prominent in GALT effector sites, that is, the intraepithelial space and LP, but numbers recovered quickly in LP. Changes in cell numbers in Peyer patches, GALT inductive sites, were subtle but persistent. Gut I/R reduced B cell numbers in Peyer patches; αβ T cell receptor (TCR)+, γδTCR+, CD8+, and B cell numbers in the intraepithelial space; and γδTCR+, CD8+, and B cell numbers in the LP, in comparison with the sham or control group. There were no significant differences in respiratory tract immunoglobulin A levels between the I/R and sham groups. Intestinal immunoglobulin A was elevated on day 1 in the I/R group, with no significant difference after day 2 in comparison with the sham group. CONCLUSIONS:Despite the maintained mucosal immunoglobulin A level, gut I/R markedly reduces GALT cell numbers, with changes in lymphocyte phenotypes. These alterations may be associated with increased morbidity due to infectious complications after severe surgical insults.