The reported severity and duration of hypogammaglobulinemia differs amongst adult populations receiving CD19-directed therapy; in one study, about half of patients had IgG >400mg/dL at the 1-year time point (26) after BCMA-directed CAR T-cell therapy, IgG<300 mg/dL in 70% of patients between 30–90 days and in 41% of patients after 1 year. Here, CD19 is linked to Decreased circulating immunoglobulin concentration.