Parenteral feeding depletes pulmonary lymphocyte populations.

backgroundThe effect of parenteral nutrition (PN) on lymphocyte mass in the lung is unknown, but reduced mucosal lymphocytes are hypothesized to play a role in the reduced immunoglobulin A-mediated immunity in both gut and lung. The ability to transfer and track cells between mice may allow study of diet-induced mucosal immune function. The objectives of this study are to characterize lung T-cell populations following parenteral feeding and to study distribution patterns of transferred donor lung T cells in recipient mice.

methodsIn experiment 1, cannulated male Balb/c mice are randomized to receive chow or PN for 5 days. Lung lymphocytes are obtained via collagenase digestion, and flow cytometric analysis is used to identify total T (CD3+) and B (CD45/B220+) cells. In experiment 2, isolated lung T cells from chow-fed male Balb/c mice are pooled and labeled in vitro with a fluorescent dye (carboxyfluorescein diacetate succinimidyl ester [CFSE]), and 1.1 x 10(8) CFSE+ cells (3.1 x 10(6) T cells) are transferred to chow-fed Balb/c recipients. Cells recovered from recipient lungs and intestinal lamina propria (LP) are analyzed by flow cytometry to determine CFSE/CD3+ T cells at 1, 2, and 7 days. In experiment 3, cells are transferred to PN-fed recipients.

resultsIn experiment 1, PN significantly decreases lung T- and B-cell populations compared with chow feeding. In experiment 2, CFSE+ T-cell retention is highest on day 1 in lung and LP, and decreases on day 2. Cells are gone by day 7; 98.1% of retained donor lung T cells migrate to recipient lungs and 1.9% to the intestine on day 1. Similar results are seen in experiment 3 after transfer of cells to PN-fed recipients.

conclusionsPN reduces pulmonary lymphocyte populations consistent with impaired respiratory immunity. Transferred lung T cells preferentially localize to recipient lungs rather than intestine with maximal accumulation at 24 hours. Limited cross-talk of transferred lung T cells to the intestine indicates that mucosal lymphocyte traffic might be programmed to localize to specific effector sites.