MATURATION OF HUMAN MYELOMONOCYTIC LEUKEMIA-CELLS FOLLOWING LIGATION OF THE LOW-AFFINITY RECEPTOR FOR IGE (FC-EPSILON-RII CD23)

The regulation of the low affinity receptor for IgE (FcepsilonRII/CD23) expression and its role were investigated in U937 cell line and in leukemic cells from a patient (Amb) with acute myeloblastic leukemia. Both cell populations were CD23- but could acquire CD23 expression following treatment with IL-4. CD23+ cells, however, remained blastic and did not show any significant phenotypical and functional modifications. Following ligation of the CD23 on U937 and Amb cells by anti-CD23 mAb, these leukemic cells differentiated into mature monocyte/macrophage-like cells. CD23 ligation promoted the expression of the monocyte marker, CD14, increased the expression of the common beta chain of the LFA-1 family (CD18), and down-regulated the expression of the promonocytic marker CD33. Morphological and phenotypical changes were associated with functional modifications as CD23 ligation allowed the acquisition of the oxidative metabolism in leukemic cells as revealed by luminol-dependent chemiluminescence. As in mature monocytes, CD23 ligation induced an accumulation of intracellular cAMP in leukemic cells. These data indicate that ligation of CD23 may induce the maturation of myelomonocytic cells into monocytic-like cells.