Indications for immunoglobulin replacement immediately prior to and for the first 3 months after CD19-targeted CAR–T-cell therapy. We suggest consideration of prophylactic immunoglobulin treatment prior to and after CD19-targeted CAR–T-cell therapy in patients with severe hypogammaglobulinemia (serum IgG <400 mg/dL). Higher thresholds can be considered in patients with serious or recurrent infections. Beyond the first 3 months after CD19-targeted CAR–T-cell infusion, we recommend consideration of prophylactic immunoglobulin treatment in patients with IgG ≤400 mg/dL and serious, persistent, or recurrent bacterial infections. Additionally, continuation of immunoglobulins could be considered in patients with IgG ≤400 mg/dL and persistent B-cell aplasia (≤20 cells per mm³ of CD19⁺ or CD20⁺ normal B cells in peripheral blood leukocytes). Reproduced from Hill et al⁴⁹  with permission from Elsevier.