Generation of a hematopoietic cDNA microarray. (A) Two cDNA libraries enriched for T-cell– and erythroid-specific transcripts, respectively, by SSH were spotted onto glass slides (hematopoietic microarray) and hybridized with Cy5-labeled cDNA derived from I/11 erythroid cells (red) and Cy3-labeled cDNA derived from CD4⁺ T cells (green). Only a small, typical section of the microarray containing approximately 9000 clones is shown. (B) The I/11 erythroid progenitors were factor deprived for 4 hours and subsequently restimulated with Epo, SCF, and either Dex or the GR antagonist ZK for 2 hours. Cy3-labeled cDNA was generated from Epo/SCF/ZK–treated cell samples; Cy5-labeled cDNA from Epo/SCF/Dex–treated cells and both labeled cDNAs were hybridized to the hematopoietic microarray. In a control experiment, the cyanin dyes for labeling of the cDNAs were exchanged (Dex-Cy3 and ZK-Cy5). Some typical clones up- or down-regulated by Epo/SCF/Dex treatment as compared with Epo/SCF/ZK are boxed.