Figure 6. Sensitivity testing of the model using the CD4⁺ T lymphocyte PP assumption.

Key assumed biological parameters in our model were varied in order to test the rigor of the prediction that CD8 depletion causes a relatively small change in rate of viremia decay. The lifetime of an activated CD4⁺ T lymphocyte (ActCD4life) was varied over 4, 7, or 15 days. The basic reproductive rate for infected cells (number of newly infected cells resulting from an infected cell in the absence of immune clearance, R₀) was varied over 8, 10, and 15. The eclipse period for an infected cell was varied over 1, 2, and 2.5 days. The factor for rate of CTL activation and killing of infected cells (α = κ) was varied over 10⁻⁸, 10⁻⁷, and 5×10⁻⁷. The graph plots the predicted % change in decay rate caused by CD8 depletion for each set of the 81 possible combinations of these parameters, varied in order of listing. Predicted decay rates of <5% are shown in blue dots, 5–10% in green dots, and >10% in red dots.