Feasibility of Flow Cytometry Analysis of Gastrointestinal Tract-Residing Lymphocytes in Hematopoietic Stem Cell Transplant Recipients

The feasibility of lymphocyte isolation and flow cytometry using a single endoscopic biopsy specimen from the gastrointestinal tract of patients who have undergone hematopoietic stem cell transplantation has not been investigated. We acquired 51 endoscopic biopsy specimens from the gastrointestinal tract of 35 patients. We divided the flow cytometry samples into two groups: group A, successful lymphocyte isolation (n=24), and group B, incomplete isolation (n=27). We compared the backgrounds of the samples between the groups to reveal crucial elements in the successful isolation of lymphocytes residing in the gastrointestinal tract. Comparison between the groups revealed lymphocyte isolation success rates differed between biopsy sites. Isolation was most successful in samples from the duodenum (8/9, 88.9%), followed by the ileum (4/8, 50.0%), large intestine (4/11, 36.4%), and stomach (8/23, 34.8%). Tacrolimus was used more frequently in group B (92.6%) than in group A (62.5%) (p=0.015). Logistic regression analysis revealed that isolation from the duodenum or ileum was a significant factor for successful isolation, while tacrolimus use was not statistically significant. In conclusion, the duodenum and ileum are more suitable sites than the stomach and colorectum for acquiring samples for flow cytometry.