Although both memory and naïve CD4 + T cells co-cultured with IEC still showed greater infectivity than those CD4 + T cells cultured alone (Fig. 1D, p < 0.0001), the increases in infection for memory T cells were much higher than for naïve T cells: IEC − cocultures increased infection by > 10% on average in memory T cells compared with 1.5% in naïve T cells; likewise, IEC + cocultures increased infection by > 15% on average in memory T cells compared with 2% in naïve T cells. Here, CD4 is linked to infection.