Figure 3.

A cell-in-cell selection model. We propose this model according to the reports that immature thymocytes penetrate into thymocyte nursing cells (TNCs) for nutrition and maturation. Accordingly, effector cells (like immature thymocytes) enter into target cells (TNCs) to form cell-in-cell structures. After cell-in-cell interaction, some internalized effector cells can be released with new properties (low panel). The others are trapped in the vacuole and energized or eliminated inside target cells (upper panel)