CD19 and acute lymphoblastic leukemia: Using this method, the B-ALL cell lineage is currently defined as: (i) ‘pro–B-ALL’, when the cells originate from early pro–B lymphoblasts that express CD19 and CD38 at the plasma membrane; (ii) ‘common B-ALL’, when the cells originate from late pro–B lymphoblasts or intermediate B-cell precursors, as identified by the expression of CD19, CD38, CD10, and CD79a at the plasma membrane; and (iii) ‘pre–B-ALL’, when the cells originate from more committed progenitors defined as pre–B lymphoblasts that express CD19, CD38, CD10, CD79a, CD20, CD22, and immunoglobulins at the plasma membrane7.