In memoriam Philip Seiden

Philip Seiden, a physicist and one of the fathers of the IMMSIM model of the immune system, died in New York, April 21, 2001.

Philip Seiden At ZiF's "The Sciences of Complexity", he shared the responsibility for the Immunology group. He had participated with enthusiasm in Symposium 2 - Theory in Immunology (October 1999), and had been expected to join the March working team. He had bought the ticket from New York, but the rapidly developing symptoms of heart failure prevented him from boarding the flight.

Philip Seiden had worked from 1960 at IBM's Thomas J. Watson Research Center, upstate New York, where he held top management positions (director of Physical Sciences, director of General Sciences) and made important contributions in Astrophysics (notably, a percolation model of galaxies formation) and solid state Physics. In 1986, when I was a "mouse sticking Immunologist", we met serendipitously. Hence, curiosity, friendship and cooperation developed, quite drastically changing both our scientific orientations. IMMSIM, a cellular automaton simulating the immune system, began as a mathematical game and progressively developed into a serious tool, trying to represent/understand the complexity of immune recognition and control. Like often in Nature, an improbable encounter had unforeseen effects.

Most of the merit for realizing thirteen years of continuous intellectual stimulation is found in Philip's brightness, flexibility, skills with computer languages, but especially, openness and mental honesty. Every new and daring expansion of the model became possible in his hands. IMMSIM's didactic potential was developed at Princeton University, where scores of students will be missing his good humoured challenges.

This is a loss to the community of theoretical immunologists that will be felt for long times and many continents.

Franco Celada