A new study published in The Turkish Journal of Gastroenterology evaluated immune cell infiltration in rectal and ileal biopsy specimens of patients with irritable bowel syndrome (IBS) and compared it with those of healthy controls. This study included 36 patients with IBS (15 with diarrhea and 21 with constipation) and 16 healthy volunteers, who underwent ileocolonoscopy and ileal/rectal biopsy. Rectal and terminal ileal biopsy specimens were evaluated for mucosal immune cell infiltration using immunohistochemical analysis. The findings showed that CD3+ and CD4+ cell counts in rectal and terminal ileal biopsy specimens were lower in the IBS group than in controls. On the other hand, there was no statistically significant difference between the IBS and the control group with respect to serotonin positivity or counts of intraepithelial lymphocytes (IEL) and CD20+ and CD8+ cells. A subgroup analysis displayed a higher number of IEL in rectal biopsy specimens of the diarrhea dominant group. Furthermore, in the IBS subgroups, immune cell counts in terminal ileal and rectal biopsy specimens showed a positive correlation. Hence, the findings suggested that there is no significant mucosal inflammation in homogeneous groups of patients with IBS. It was stated that rectal biopsies may be sufficient for the evaluation of inflammation in IBS.