Following infection, the proportion of effector CD4+ T cells with low Id3 expression significantly increased, but as the infection was cleared, upward of 90% of the remaining memory cells expressed Id3-GFP (Fig. 1 A and B), with a greater absolute number of Id3-expressing cells surviving the contraction phase and persisting to memory time points (Fig. 1C). The gene discussed is CD4; the disease is infection.