Prospective data on immunoglobulin replacement after CD19-targeted CAR-T cell therapy is currently unavailable, however, as severe hypogammaglobulinemia may increase risk for respiratory tract and other infections with encapsulated bacterial organisms (e.g., Streptococcus pneumoniae and Haemophilus influenzae type b), testing of serum IgG levels frequently after CD19-targeted CAR-T therapy, and administration of intravenous immunoglobulins to keep levels of IgG > 400 mg/dL may be considered until long term data on the association of hypogammaglobinemia with infections is well established. Here, CD19 is linked to infection.