Figure 9. Proposed model for the development of early-memory precursors.

Naive Fucci CD8⁺ T cells are mKO2^hi small cells in the G₀ phase with high CD62L expression levels. Following virus infection, antigen-activated CD8⁺ T cells enter the cell cycle and downregulate CD62L expression. During the vigorous expansion phase, most of the activated CD8⁺ T cells increase in size and are found as mAG⁺ or DN cells reflecting fast cell divisions accompanied by intermediate CD62L levels (around days 4–6). On day 7 p.i., the proliferative CD8⁺ T-cell pool starts to segregate into the smaller CD62L^hi mKO2⁺ central memory precursor cells, and the larger CD62L^lo phenotype cells, which maintain proliferation and differentiation into terminal effector cells.