Computer simulation of the cellular immune response to malignant lymphoid cells: logic of approach, model design and laboratory verification.

A computer model was constructed to simulate the lymphocyte-mediated destruction of line Ib malignant lymphoid cells (Ib cells) as they circulated through the major tissue compartments of immune syngeneic C58 mice. The technique of discrete-event simulation was used to account for the arterial and venous circulation of blood-borne Ib cells through the lung, spleen, liver, and carcass. Simulation was carried out by means of IBM computer program 360, using the technique of General Purpose System Simulation. The parameters analysed were the mean residence times of viable and killed Ib cells in each tissue compartment, the rate or proliferation of Ib cells, the rate of generation of cytotoxic splenic lymphocytes, the rate of lysis of 51Cr labelled Ib cells, and the organ-specific rate constants for target cell kill. Direct laboratory measurements of these parameters validated the model and made it possible to calibrate computer simulations by the technique of best-fit analysis. The computer modelling technique accurately simulated the growth of viable Ib cells in vivo and the retention times of 51Cr in the spleen, lung, liver and carcass when viable or heat-killed Ib cells were inoculated intravenously (i.v.) into normal and immune mice. Computer simulations quantitatively defined the mean residence times of viable and heat-killed Ib cells in the major tissue compartments and the mean rate constants for target cell lysis in such compartments. The applicability of modelling approach to an analysis of immunological phenomena is discussed.