CTLA4 and Nasal polyposis: In the nasal polyp tissues, the reciprocal control of the DCs and T cells, through CD40/CD40L, B7-CD28/CTLA-4 co-stimulating molecules, the high levels of IL-4 and IL-10 and the low expresson levels of IL-12, induced an imbalance in the proportion of the Th1/Th2 cells and caused the predominance of Th2 cell cytokines.