The Hill function, fDj (I10), in Eq 7 describes the I10 down-regulation of the process for I4 or I6 production by TD (Fig 1). Thus, for I4 and I6, fjD(I10)=11+(I10KIi,I10)2(9) whereas fD (I10) = 0 for other cytokines, whose population dynamics are governed by Equations A-G given in S1 File. For example, Eqs 10–11 describing the dynamics of I6 and I10 are given by dI6dt=kI6,M1M111+(I10KM1,I10)2+kI6,TDTD11+(I10KI6,I10)2−dI6I6(10) dI10dt=(kI10,M2M2+kI10,TgTg)11+(I10/KI10,I10)2−dI10I10(11)