Microarray profiling of naive normal PBMCs, activated normal PBMCs, and leukemic LGLs using gene- and theme-based approaches. (A) Differential expression of genes in normal PBMCs following activation. A total of 775 genes are expressed differentially (at least 2-fold change and 1% FDR) following activation. EASE analysis of 2 phenotypes shows statistically significant up-regulation of genes belonging to GO categories “regulation of programmed cell death” and “positive regulation of apoptosis.” (B) Constitutive gene expression signature of leukemic LGLs compared with naive normal cells. A total of 174 genes were differentially expressed in leukemic LGLs compared with naive normal cells (at least 2-fold change and 1% FDR). EASE analysis of leukemic LGLs compared with naive normal cells shows significant up-regulation of genes belonging to GO categories such as immune system process, immune response, viral life cycle, viral infectious cycle, and viral genome replication. (C) Constitutive gene expression signature of leukemic LGLs compared with activated normal cells. A total of 1492 genes were differentially expressed in leukemic LGLs compared with activated normal cells (at least 2-fold change and 1% FDR). EASE analysis of leukemic LGLs compared with activated normal cells shows up-regulation of immune response–related signaling and cytotoxicity-related GO categories to be significantly up-regulated in leukemic LGLs compared with activated normal cells. Each row in the cluster image represents an individual gene, and each column represents an individual sample from LGL leukemia patient or healthy donor. The relative transcript abundance of each gene is color coded. A red color indicates high expression, black indicates intermediate expression, and green indicates low expression.