Antigen-presenting dendritic cells in ulcerative colitis

Abstract

Background. Antigen-presenting dendritic cells are the inducers and regulators of immune responses. Here, we have discussed the phenotype and function of dendritic cells in situ and their alteration during lymphocytapheresis in patients with ulcerative colitis. Methods. Dendritic cells were enriched from the peripheral blood mononuclear cells by culturing with granulocyte-macrophage colony-stimulating factors and interleukin 4 for 8 days. The function of dendritic cells was evaluated in an allogenic mixed leukocyte reaction. Flow cytometry was employed to study the phenotype of dendritic cells. Lymphocytapheresis was done by a continuous flow centrifugation technique using a CS-3000 separator. Immunohistochemical methodology was employed to detect dendritic cells at the colonic mucosa. Results. Peripheral blood dendritic cells had increased functional capacity, and these cells were matured and activated compared to dendritic cells from normal controls. CD83-positive activated and mature dendritic cells were found at the colonic mucosa from patients with ulcerative colitis. Lymphocytapheresis induced decreased function of peripheral blood dendritic cells in patients with ulcerative colitis. Also, the levels of inflammatory cytokines were reduced by lymphocytapheresis. Conclusions. Increased function of dendritic cells may be related to the inflammatory mucosal milieu found in patients with ulcerative colitis. Depletion of dendritic cells during lymphocytapheresis may downregulate the exacerbated immune response in patients with ulcerative colitis.