CTLA4 and Behcet disease: However, this result is partially contradictory to that of Sim et al. [27] who reported a reduced expression of CTLA-4 in CD4+ T cells in patients with active Behçet's disease, with no difference in the production of sCTLA-4, leading to subsequent increase in Th1 cell proliferation and a tendency to the development of Behçet's disease.