CD4 + T cells with a cytolytic phenotype (CD4 + CTLs) that secrete pro‐fibrotic cytokines including IL‐1beta, TGF‐beta, and interferon‐gamma are viewed as essential to the pathophysiology of IgG4‐RD (Maehara et al., 2017; Mattoo et al., 2016). Here, CD4 is linked to immunoglobulin G4-related sclerosing disease.