Used in research and development of targeted cancer therapies, particularly for B-cell malignancies such as non-Hodgkin's lymphoma and acute lymphoblastic leukemia. Binds specifically to the CD19 antigen expressed on B-cells, enabling the study of antibody-drug conjugates, bispecific antibodies, and CAR-T cell therapies. Serves as a reference standard in immunological assays, flow cytometry, and binding affinity studies to evaluate performance of therapeutic antibodies. Supports quality control and comparability assessments during biosimilar development and manufacturing.