To evaluate the contribution of the FasL:Fas pathway in our model system, we conducted mixed AT/RC experiments with B6 vs. Faslpr (“B6.lpr”) recipients and observed a preferential reduction of aged IIo CD8+TE expansions in the B6.lpr hosts that was especially pronounced following chronic LCMV cl13 infection (Fig 3D). The gene discussed is FASLG; the disease is infection.