CD4 and immunoglobulin G4-related sclerosing disease: The proportion of expanded (frequency ≥ 0.01%) and coding degenerated (coding degeneracy level ≥ 2) clones was significantly higher in IgG4-RD patients (Fig. 2c) (healthy controls, 0.209% ± 0.103% [outlier included], 0.167% ± 0.022% [HC-1 excluded as outlier]; IgG4-RD patients, 0.259% ± 0.053%; Welch’s t test, p = 0.313 [outlier included], p = 0.001 [outlier excluded]), which suggests the antigen-driven clonal expansion of CD4+ T cells in IgG4-RD.