Providing CD4 help again to memory CD8 T cells that had not undergone an appropriate secondary response restored memory cell expansion during the tertiary response. Mice that had not been provided with CD4 help during the secondary response were immunized with male or female H60 cells as a tertiary challenge. The percentage of H60-tetramer⁺ CD11a⁺ CD8 T cells was plotted after periodic staining of PBLs from the immunized mice (3 mice per group). Representative FACs data from 3 independent experiments (gated for CD8⁺ cells) are shown.