Figure 6.

Models for the development of T-cell memory. (a) Primary and memory populations of T cells may derive from different naive precursors. The TCR use of the primary and memory populations would not be closely related. (b) Naive T cells differentiate to form a primary population. A minority of these cells persist into memory, while the majority die. The TCR use of the memory population would be identical to, or possibly more restricted than, that of the primary population. (c) Naive T cells differentiate to form an intermediate core cell from which both an expanded primary population (destined to die) and a memory population may derive. The TCR use of the memory population would be similar to that of the primary population, but relative depletion of the clonotypes most expanded during the primary response might occur.