[1207] Distinct Expression Patterns of CD123 and CD34 on Hematogones and Blasts in Precursor B-Cell Acute Lymphoblastic Leukemia

NM Hassanein, PJ Buckley, AS Lagoo. Duke University Medical Center, Durham, NC

Background: Bone marrow derived normal B-cell precursors (hematogones) and blasts in precursor B-cell acute lymphoblastic leukemia (B-ALL) share many immunophenotypic properties. Distinguishing between these two populations following treatment or during early relapse of precursor B-ALL can be challenging.
Design: Using four color flow cytometry, we examined the expression patterns of two hematopoietic stem cell antigens, CD34 and CD123 (interleukin-3 receptor alpha) on hematogones in 75 regenerating bone marrow samples without a diagnosis of precursor B-ALL and in 40 cases of precursor B-ALL. The hematogones were identified by their characteristic low side scatter, and CD45, CD19 and CD10 expression. CD34 and HLA-DR expression on these cells was also analyzed.
Results: CD123 was expressed only on the more mature (moderate CD45, CD34-, DR+) fraction of hematogones and the less mature hematogone fraction (dimmer CD45, CD34+, DR+) did not express CD123 on most cells. In contrast to this discordant expression of CD34 and CD123 on hematogones, leukemic blasts in most cases of precursor B-ALL showed concordant expression of these antigens. Thus in 31 of 40 cases (77.5%) the blasts expressed both CD34 and CD123 and in 5 of 40 cases (12.5%) neither antigen was expressed. Only in 4 additional cases in which the blasts did not express CD34, a variable proportion of blasts (7 to 96%) expressed CD123.
Conclusions: Hematogones show a discordant expression patterns of CD34 and CD123 while blasts in most cases of precursor B-ALL show concordant expression patterns of these antigens. Among the CD19+ B-cells in the bone marrow, CD34+/CD123+ (double positive) or CD34-/CD123- (double negative) patterns can be used to identify leukemic blasts and distinguish them from the hematogones with their CD34+/CD123- or CD34-/CD123+ discordant expression patterns.
Category: Hematopathology

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 172, Wednesday Afternoon