Suppression of intestinal mucosal natural killer cells by corticosteroids.

BACKGROUND: Corticosteroid therapy of patients with inflammatory bowel disease can give rise to systemic side-effects. Budesonide is a topically acting corticosteroid with low systemic bioavailability and is efficacious in the treatment of inflammatory bowel disease. Natural killer cells were previously found to be altered, both systemically and locally, in patients with inflammatory bowel disease. Modulatory effects of budesonide, prednisolone, dexamethasone, and cortisol on peripheral blood NK cells have already been described, but have never been assessed on mucosal NK cells from the intestine. METHODS: The effect of the synthetic corticosteroids prednisolone and budesonide, the endogenous corticosteroid cortisol, and adrenocorticotropic hormone was analysed on NK cells isolated from the lamina propria of human intestinal resection specimens. RESULTS: The three corticosteroids suppressed intestinal NK cell activity, not only during the cytotoxicity assay, but also after pre-incubation of the lamina propria mononuclear cells. ACTH, however, did not affect the activity of intestinal NK cells. We previously showed that corticosteroid-suppressed peripheral blood NK cell activity could be restored in vivo, but not in vitro, by the administration of ACTH. In the present study, the in vitro incubation of budesonide- or prednisolone-suppressed mucosal NK cells with cortisol, alone or combined with ACTH, did not revert the suppressed NK cell activity. These findings are similar to our previous observations with peripheral blood NK cells. CONCLUSIONS: Intestinal mucosal NK cells can be suppressed by systemically as well as locally acting corticosteroids. This suppression in NK cell activity is not reversed by incubation with cortisol and/or ACTH.

Budesonide and prednisolone suppress peripheral blood natural killer cells in Crohn's disease.

AIM: To study the effect of oral budesonide and prednisolone on peripheral blood natural killer (NK) cell activity in patients with active ileocaecal Crohn's disease (Crohn's disease activity index, CDAI > or = 200). METHODS: One group of patients was treated for 10 weeks with oral budesonide (n = 9; 9 mg/day), and another group of patients for the same period with prednisolone (n = 9; 40 mg/day). Budesonide was tapered to 6 mg/day after 8 weeks and prednisolone after 2 weeks to 5 mg/day in the last week. Before treatment, and at 2, 4 and 10 weeks of treatment, natural killer cell activity was determined with a 51Cr release assay, and the number of CD16+ NK cells by Fluorescence activated cell sorter (FACS) analysis. RESULTS: Budesonide, as well as prednisolone treatment, significantly decreased natural killer cell activity at weeks 2 and 4. This decrease was found to be accompanied by a similar decrease in the number of CD16+ NK cells. At 10 weeks, natural killer cell activity had almost returned to pre-treatment levels in the budesonide group and was significantly higher than pre-treatment levels in the prednisolone group. Disease activity was significantly decreased in all patients at week 2 until the end of the trial period. CONCLUSION: Both budesonide and prednisolone treatment suppress peripheral blood natural killer cell activity of patients with active ileocaecal Crohn's disease by decreasing the numbers of CD16+ NK cells in the circulation.