As precursors of T lymphocytes develop in the thymus and infiltrate into the bone marrow [32] and B lymphocytes or myeloid cells mainly develop in the bone marrow, it is not surprising that Sema4D expression is lower in BMMCs of T-ALL patients than in the BMMCs of B-ALL or AML patients. The gene discussed is SEMA4D; the disease is acute myeloid leukemia.