#### Alan Perelson, Gérard Weisbuch

Paper #: 95-06-056

The immune system is a complex system of cells and molecules that can provide us with a basic defense against pathogenic organisms. Like the nervous system, the immune system performs pattern recognition tasks, learns and retains a memory of the antigens that it has fought. The immune system contains more than $10^7$ different clones of cells that communicate via cell-cell contact and the secretion of molecules. Performing complex tasks such as learning and memory involves cooperativity among large numbers of components of the immune system and hence there is interest in using methods and concepts from statistical physics. Furthermore, the immune response develops in time and the description of its time evolution is an interesting problem in dynamical systems. In this paper, we provide a brief introduction to the biology of the immune system and discuss a number of immunological problems in which the use of physical concepts and mathematical methods have increased our understanding. The field of theoretical immunology has been growing rapidly and we have not attempted to review all the work that has been done. This article is thus primarily a personal perspective centered on our own contributions to the field with briefer descriptions and references given to the work of others.