For example, in Th1 compared to in Th2 cells, a higher JAK-STAT1/2 pathway activity is necessary for the Th1 role to activate CD8+ T cells, for example in viral infections [9], while a high PI3K pathway activity is required for the expression of the TBET transcription factor, essential for Th1 function [8]. The gene discussed is STAT1; the disease is viral infectious disease.