Inflammatory bowel diseases
Natural Killer (NK) cells play an important role in protecting the host by killing cancer and virus-infected cells. However, they also have the potential to kill body’s own ‘altered’ cells and contribute towards tissue destruction. Crohn disease is a chronic inflammatory disease affecting gastrointestinal tract especially terminal part of ileum and colon in children and adolescents. In order to investigate whether NK cells may play a role in the immunopathogenesis of this disease, we compared the expression of KIR and non-KIR receptors, activation status and cytotoxic activity of peripheral blood NK cells between Crohn disease patients and age-matched healthy control subjects. The investigations were performed ex vivo directly on whole blood taken from the patients as well as from the control subjects. Our results show that NK cells from CD patients expressed higher levels of activating KIR as well as other non-KIR activating receptors vis-à-vis healthy control donors.. The expression of inhibitory KIR and other non-KIR receptors tended to decrease compared to healthy donors. The NK cells from the patients expressed higher levels of CD69, NKG2D and IL-23R. NK cells from the patients also expressed increased levels of different gut-homing integrin molecules. They also had higher expression of CD107a on their surface. The expression was higher constitutively as well as in response to incubation with NK-sensitive K562 cells. Furthermore, the NK cells from the patients showed higher cytotoxic activity against NK-sensitive target cells. Therefore, they are very likely to play a role in the immunopathogenesis of the disease.