The expression of the hematopoietic transcription factors GATA-1, GATA- 2, and GATA-3 was studied in eosinophils and basophils. Eosinophils express mRNA for GATA-1, GATA-2, and GATA-3. Basophils express GATA-2 and GATA-3. Treatment of HL-60 eosinophilic sublines with either interleukin-5 or butyric acid increased the expression of GATA-1 mRNA concomitant with the expression of eosinophil-specific genes, whereas levels of GATA-2 mRNA remained relatively constant. The presence of mRNA for these proteins in eosinophils and basophils suggests that gene transcription in these lineages may be regulated by GATA-binding proteins.

Suspension cultures of human umbilical cord blood mononuclear cells supplemented with c-kit ligand-containing additives give rise to a mixture of cells belonging to several lineages. Among those that differentiate in quantity are mature basophils, immature mast cells, and neutrophilic myelocytes. We used an ultrastructural immunogold method to detect the Charcot-Leyden crystal (CLC) protein, an eosinophiland basophil-specific protein, to study cells that were obtained at sequential times from 3 to 14 weeks in culture. Basophils (and eosinophils, which were present in smaller numbers) labeled for the CLC protein; mast cells did not. The labeled basophil subcellular sites included formed intragranular, cytoplasmic and nuclear CLCs, cytoplasmic particle-filled and homogeneously dense granules, cytoplasm, nucleus, plasma membrane, and cytoplasmic and IntroductionHuman basophils and mast cells can now be reliably induced to develop in vitro from their agranular precursors which are present in cord blood (1-6). Initially, these studies were done with supplements of various cell-conditioned media now known to contain a basophil growth factor, interleukin-3 (IL3) (l), or a mast cell growth factor, the c-kit ligand [also called stem cell factor (SCF)] (5,6). Some of these studies were also done with cord blood cells cocultured with mouse 3T3 fibroblasts (3,4 repeated with these reagents. In all of these cultures, ultrastructural criteria were used to assign immature and mature cells to the appropriate lineages (1-5) (AM Dvorak et al., unpublished data).Charcot-Leyden crystals (CLCs) are hexagonal, bipyramidal structures originally described in eosinophil-rich disorders (7,8). CLC protein is the sole protein constituent of CLCs purified from human eosinophils; it expresses lysophospholipase activity, forms these characteristic crystals, and comprises an estimated 7-10% of total cellular protein in the eosinophil (9-12). CLCs and the CLC protein, once considered unique to the eosinophil lineage, have also been found in human basophils (2,13,14). Using an ultrastructural immunogold method, we have defined the subcellular locations of the CLC protein in quiescent peripheral blood eosinophils (15) and basophils (16) (17-19). Although the cellular function(s) of this lysophospholipase is still obscure, the presence of such large quantities of this enzyme in eosinophils and basophils suggests an important role in normal or pathological events associated with these lineages. The recent cloning of the gene for the CLC protein (20) and expression of the protein product (12) should aid future studies of the biological properties of this unique basophil and eosinophil constituent.Human mast cells, in contrast to basophils, do not stain for the CLC protein by light microscopy (21). Since we noted an admixture of lineages in suspension cultures of cord blood supplemented with c-kit ligand-containing additives, we examined these cells for CLC protein using an immunogold method to detect this protein.We found that mature basophils that ...

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