Ulike the constitutively expressed CD28, ICOS has to be de novo induced on the T-cell surface, while GL50 is expressed on B cells and macrophages or induced on fibroblasts etc.

• ICOS主要表达在活化的T细胞上，而GL50可表达在活化的B细胞、巨噬细胞或诱导表达于成纤维细胞等多种细胞表面。