USING LAZY EVALUATION TO SIMULATE REALISTIC-SIZE REPERTOIRES IN MODELS OF THE IMMUNE-SYSTEM

We describe a method of implementing efficient computer simulations of immune systems that have a large number of unique B- and/or T-cell cl ones. The method uses an implementation technique called lazy evaluati on to create the illusion that all clones are being simulated, while o nly actually simulating a much smaller number of clones that can respo nd to the antigens in the simulation. The method is effective because only 0.001-0.01% of clones can typically be stimulated by an antigen, and because many simulations involve only a small number of distinct a ntigens. A lazy simulation of a realistic number of clones and 10 dist inct antigens is 1000 times faster and 10 000 times smaller than a con ventional simulation-making simulations of immune systems with realist ic-size repertoires computationally tractable. (C) 1998 Society for Ma thematical Biology.