IMMUNOPHENOTYPIC ANALYSIS OF HL-60 CELLS DURING BASOPHILIC DIFFERENTIATION

Differentiation along specific myeloid lineages may be accompanied by characteristic cell surface marker changes. We have examined leukemic HL-60 cell changes under conditions which induce basophilic differenti ation. An increased surface expression of CD35, CD11b, and decreased e xpression of CD15 was found by flow cytometry during the 5-day inducti on period. Further investigation revealed two cell populations after 5 days in vitro: (i) a CD35-positive population (61% of cells present) containing a significant number of CD15-negative cells, and (ii) a CD1 5-positive/CD35-negative population. The CD35-positive subset appears to account for the majority of the basophilic cells induced under thes e conditions, as measured by histamine content and metachromatic stain ing. In addition, this subset contains a small number of early monocyt ic cells (CD14 and CD23 positive). The expression of CD11b is variably found on the CD15-positive/CD35-negative subset of induced cells. The se results suggest that CD35 and CD15 surface immunophenotyping can be used to map steps involved in myeloid development. A role for CD35 an d CD15 in early basophil differentiation is proposed.