Scientists have identified a protein that helps the immune system recognize and destroy leukemia cells. The protein, CD19-ligand (CD19-L), is located on the surface of T-lymphocytes, and the researchers report that it is the first CD19-specific recombinant human protein with potent anti-leukemic activity against B-lineage acute lymphoblastic leukemia (ALL). ALL is the most common form of childhood cancer and the second most common form of acute leukemia in adults.

Fatih Uckun, MD, PhD, of the University of Southern California Keck School of Medicine and the Norris Comprehensive Cancer Center, and colleagues explained the significance of CD19-L in their paper, published online ahead of print by British Journal of Haematology: The newly discovered element allows T-lymphocytes to selectively bind to the CD19 receptor on the surfaces of B-lineage leukemia cells and—most important—on leukemic stem cells responsible for the survival and expansion of the leukemia cell population. Cell death occurs after CD19-L binds to leukemia cells. Because CD19 is absent on red cells, T-cells, and normal bone marrow stem cells but abundantly expressed on leukemia cells in B-lineage ALL, it is a good therapeutic target.

Dr. Uckun’s team bioengineered a highly purified liquid formulation of the human CD19-L protein, which showed selective binding to leukemia cells and destroyed them within 24 hours. These results were observed even among leukemia cells that were highly resistant to both standard chemotherapy agents as well as radiation.

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