Indeed, anti-CD19 therapy with inebilizumab is currently being tested in a clinical trial (clinicaltrials.gov: NCT04540497) and obinutuzumab—a humanized anti-CD20 monoclonal antibody with higher B cell depleting activity compared with rituximab—has been proven effective in IgG4-RD [17, 18]. Here, CD19 is linked to immunoglobulin G4-related sclerosing disease.