Figure 8

Immune system dynamics for re-infection when viral antigen is eliminated compared to when it persists. Here, the same re-introduction protocol as for Fig. 5 was followed. (A) Antigenic persistence (red and blue lines) keeps CTL _P abundance continually high regardless of when antigen is re-introduced repeatedly at t = 1000, 3000, 6000, and 9000 days (blue line) or only once at t = 9000 days (red line). Antigenic elimination (with slow rates of CTL _P decline, b = 0.001 day^-1, high immune responsiveness, c _i = 0.1, and assumed v _ext = 0.015) demonstrates that re-expansion requires time for individuals to mount an effective immune response (yellow and black lines). (B and C) There is also a proportional, positive growth in the abundance of CTL _E cells that follows directly from the expansion of CTL _P cells after single instance of re-introducing viral antigen (B) assuming antigen is eliminated (black line) or antigen persists (red line), as well as repeated re-introduction (C) assuming antigen persistence (blue line) and antigenic elimination (yellow line).