Gene expression patterns of selected functional groups. Gene expression levels were calculated using MAS, RMA, and dChip, normalized using the associated algorithms, and filtered using GeneSpring. Genes with more than 2-fold change in expression compared to baseline (0 hours) were selected. Only those genes selected irrespective of normalization method were further analyzed. Genes were analyzed by functional group and cluster, which identified a number of differing patterns of gene expression in each group. The resulting groups of genes were therefore further refined into those related by function ([A] transcription factors, [B] cell cycle genes, [C] cytokines, [D] cytokine receptors, [E] chemokine receptors, and [F] cytotoxic effectors) and by change in expression during the primary response. Graphs represent the mean expression level of genes within each group as generated using RMA. Histograms indicate the number of genes contributing to each group.