Alteration of natural killer cell subsets (two color analysis) and their activity in peripheral blood in inflammatory bowel disease.

The natural killer (NK) activity and NK cell subsets in peripheral blood were evaluated in patients with inflammatory bowel disease (IBD), by using 51Cr release cytotoxicity assay and two color flowcytometry analysis. The peripheral blood NK activity was significantly lower in IBD than that in normal controls. This decrease of the NK activity was independent on the disease activity of IBD but dependent on the steroid medication. The total population of NK cells (Leu 7+ or 11c+ cells) did not change in IBD as compared with those of normal controls. However, the proportions of Leu7+11c- cells and Leu7-11c+ cells in IBD were higher and lower, respectively as compared with those of normal controls. These findings suggest that the maturation step of NK cell lineages might be impaired in IBD. The decrease of NK activity in IBD was supported by the change in the proportion of NK cell subsets described above. It was thought that such a change in NK cell subsets might be a specific finding in IBD patients, because it was not observed in patients with non-IBD colitis.