Numerical solution by LMMs of stiff delay differential systems modelling an immune response

We consider the application of linear multistep methods (LMMs) for the numerical solution of initial value problem for stiff delay differential equations (DDEs) with several constant delays, which are used in mathematical modelling of immune response. For the approximation of delayed variables the Nordsieck's interpolation technique, providing an interpolation procedure consistent with the underlying linear multistep formula, is used. An analysis of the convergence for a variable-stepsize and structure of the asymptotic expansion of global error for a fixed-stepsize is presented. Some absolute stability characteristics of the method are examined. Implementation details of the code DIFSUB-DDE, being a modification of the Gear's DIFSUB, are given. Finally, an efficiency of the code developed for solution of stiff DDEs over a wide range of tolerances is illustrated on biomedical application model.