BACKGROUND.

Intestinal mucosa contains intraepithelial lymphocytes (IEL) and changes in IEL subsets are seen in inflammatory bowel disease or celiac disease. We aimed at investigating the intestinal IEL populations in small bowel transplanted (SBT) patients and the potential correlation with infections or rejection.

 

METHODS.

We analyzed 182 ileal mucosa biopsies from 15 SBT recipients obtained between post-transplant days +4 and +2292 and 21 biopsies from normal native intestines as controls. Epithelial cells were obtained from disruption of biopsies in a DTT + EDTA buffer, and the following populations were analyzed by flow cytometry: IEL (CD45+CD103+ infiltrating cells), NK-like cells (CD45+CD103+CD3-), T lymphocytes (CD45+CD103+CD3+) and T cells CD8+ and CD4+ subsets. Immunosuppressive therapy, infections and rejection events from paired biopsies were also collected.

 

RESULTS.

IEL infiltration in transplant biopsies remained stable along time and was similar to controls. In transplant biopsies obtained duringthe first month, T cells were the main IEL population, differing significantly from control biopsies (patients=89%, controls=81%; p=0.005). During 2^nd month post-transplant this population returned to normal values, decreasing significantly at 3^rd month(patients=57%, controls=81%; p<0.001). The opposite behavior was observed in NK-like subset, which diminished significantly in first month (patients=10%, controls=18%; p=0.005) and became the main population since 3^rd month (patients=43%; controls=18%, p<0.001). This pattern was more pronounced in patients with combined tacrolimus plus corticosteroids therapy. In T cells subsets, a decrease of CD4-CD8+ population was observed since 1^st month (patients=43%; controls=69%, p<0.001). T cells CD4+CD8- increased significantly in 3^rd month (patients=34%; controls=19%, p=0.02) and reached amaximum during second year (patients=53%; controls=19%, p<0.001). No correlation between changes in IEL subsets and infections or rejection was observed.

 

CONCLUSIONS.

NK-like lymphocytes are the main IEL subset in the intestinal graft since 3^rd month post-transplant. Evolution of IELs follows a common pattern and is independent of clinical events.