Stimulating the Itk-/- and Wt T-cells with anti-CD3 resulted in 804 differentially expressed probe-sets in Itk-deficiency (74% up- and 26% down-regulated, 68% with p < 0.05), while after anti-CD3/CD28-stimulation the number was reduced to 409 (78% up- and 22% down-regulated; 58% with p < 0.05) as depicted in Figure 1a. The gene discussed is CD28; the disease is lymphoproliferative syndrome 1.