Table 1.

Values and sources of the parameters in the mathematical model

Parameter	Biological meaning	Value	Source
αC	Rate of target-cell proliferation	3/day	12,13,19
αT	Rate of antigen-independent T-cell proliferation	5 × 10−2/day	20,21
μC	Rate of death due to competition between target cells	1·5 × 10−6 μl/day	ad hoc
μT	Rate of T-cell death due to homeostatic regulation	2·5 × 10−6 μl/day	ad hoc
βC	Killing rate of target cells by T cells	1 × 10−5 μl/day	12,13,19
βT	Rate of T-cell replication following recognition	3 × 10−5 μl/day	12
θ	Average affinity range of T-cell receptors	1 × 10−3 ÷ 1 × 10−1	12,22
γ	Maximum affinity	1 × 10−2 ÷ 3	15,19

The values of the parameters α_C, α_T, β_C and β_T are consistent with previous measurement and estimation studies on the immune response mediated by T cells.^{12,13,19–21} The values of the parameters μ_C and μ_T are selected to guarantee that the carrying capacities of the two cell populations are biologically consistent. The range of values of the parameter θ is consistent with experimental estimations of the precursor frequency of T cells,²² and it is computed through a strategy analogous to that presented in ref. 12. The values of the parameter γ are consistent with those used in refs ^15,19.