CD69 EXPRESSION ON PRIMITIVE PROGENITOR CELLS AND HEMATOPOIETIC MALIGNANCIES

CD69 is an early activation antigen of peripheral blood lymphocytes an d is constitutively expressed on a wide variety of bone marrow-derived cells. To further characterize the distribution and understand the po tential biological role of the molecule in normal and malignant hemato poiesis, we used a novel high affinity anti-CD69 mAb (UN6) and analyze d hematopoietic progenitor cells together with a panel of myeloid and lymphoid malignancies. We report that mobilized peripheral blood CD34( +) cells display detectable levels of CD69 and that the density of mem brane expression correlates with the immature phenotype CD34(bright) T hy-1(bright) cells. Furthermore, during cytokine-induced differentiati on, the expression of CD69 is moderately down-regulated. Analysis of h ematopoietic malignancies revealed that CD69 expression correlates wit h the immature myeloid phenotype. Taken together these data suggest a role of CD69 during the early phase of hematopoiesis and in the leukem ic transformation.