One-pass selection model of the germinal center reaction

For the specific purpose of the germinal center dynamics, one might be interested in a number of scenarios for the mutation selection process. It is, for example, not known whether mutation occurs during B cell replication or during transcription of the immunoglobulin gene. It is also not known whether the antigen is depleted by B cells, or by other B cell independent mechanisms. All these scenarios give qualitatively similar results, and thus here I will only present one: mutations are introduced at B cell replication, and the antigen decays exponentially with time.