CD4 and immunoglobulin G4-related sclerosing disease: However, when we took into consideration the coding degeneracy level of each clone, as an indicator of antigen-driven T cell expansion [19], we found a significantly higher proportion of expanded and coding degenerated clones in CD4+ T cells of IgG4-RD patients (Fig. 2), suggesting of antigen-driven clonal expansion in IgG4-RD.