Anti-CD19 molecule antibodies are directed against the protein encoded by the gene CD19 in humans. The gene may also be known as B4, CVID3, B-lymphocyte antigen CD19, and B-lymphocyte surface antigen B4. Structurally, the protein is reported to be 61.1 kilodaltons in mass. Based on gene name, canine, porcine, monkey, mouse and rat orthologs may also be found. Anti-CD19 molecule antibodies are directed against the protein encoded by the gene CD19 in humans. The gene may also be known as B4, CVID3, B-lymphocyte antigen CD19, and B-lymphocyte surface antigen B4. Structurally, the protein is reported to be 61.1 kilodaltons in mass. Based on gene name, canine, porcine, monkey, mouse and rat orthologs may also be found.