ART4 and viral infectious disease: In response to an acute viral infection, activated virus-specific CD4+ T cells differentiate into either TH1 or TFH cells.15,55,56 We first adoptively transferred LCMV-specific naïve SMARTA cells (expressing a transgenic T cell receptor specific for the LCMV glycoprotein epitope I-AbGP66–77) into WT C57BL/6J recipients and subsequently infected the chimeric recipients with the LCMV Armstrong strain to investigate the potential regulatory regions involved in this bifurcated differentiation at the genome level.