This event was recorded on July 29th, 2026 at Flug Forum, produced by Aspen Center for Physics, in partnership with Aspen Public Radio.
Your immune system faces a remarkable challenge: it must defend you against viruses and other pathogens it has never seen before. It solves this problem by learning. Instead of storing a fixed list of answers, it tries new approaches and remembers the ones that worked in the past. In this lecture, I will describe how the body generates an enormous repertoire of antibodies, each with a different molecular “shape,” and how infection or vaccination triggers a surprising process in which some immune cells deliberately mutate their genes to generate novel antibodies. These cells undergo cycles of mutation and competition within your lymph nodes (hence the swelling!), to generate improved variants. The result is better antibodies that bind more effectively to their targets. This is Darwinian evolution, but accelerated to the timescale of days and occurring inside your own body. I will discuss how biophysical models can help us understand this learning process, why it matters for vaccines, how failures of immune learning contribute to autoimmunity, and why immune learning might become less effective with age.
Ned Wingreen received his Ph.D. in theoretical condensed matter physics from Cornell University in 1989. He did his postdoc in mesoscopic physics at MIT before moving, in 1991, to the newly founded NEC Research Institute in Princeton. At NEC, he continued to work in mesoscopic physics, but also started research on the statistical mechanics of protein folding. Thinking about proteins led him inexorably down the path into biology. During a sabbatical at UC Berkeley in 1999, his primary focus shifted to systems biology of bacteria. Wingreen joined Princeton University as a Professor of Molecular Biology in 2004, with a joint appointment in the Lewis-Sigler Institute as of 2008. Wingreen's current research focuses on modeling the biophysics of bacteria and their viruses (phage), intracellular phase separation, and most recently immunology.