The adaptive immune system protects us from death by infection. The system relies on specific binding by a diverse repertoire of immune receptors to foreign antigens, and an effective response relies on amplification of the cells that bind well to these antigens. However, this amplification must be carefully regulated to avoid autoimmunity. One challenge is that the initial size of a clone of immune cells can be quite variable. Intriguingly, the fold expansion of such a clone is found to depend as an inverse power law on its initial size. I will discuss a simple biophysical model which naturally yields the observed power-law relation, accounts for multiple experiments on amplification, suggests optimal vaccination protocols, and highlights the dynamics of presented antigen as a key regulator of the size of an immune response. Time permitting, I will also discuss how adaptive immunity shapes the evolution of a particular human pathogen - the influenza A virus.
Host: Ben Machta