Heatmap depicting the expression levels of genes separating GWI cases from controls immediately after the exercise challenge. Immediately after the exercise stress challenge is when we expected differences between GWI cases and controls to be maximal so the most likely time to find the most striking differences. Hierarchical clustering of the 141 probe sets correlating with NK cell subset numbers at the T1 time point was used to show that 9 genes were effective in separating cases from controls. High and low expression levels are shown as red and green respectively. Dendogram at the top shows the clustering results and gene names are given on the right side.