Reassessing Germinal Centre Reaction Concepts

To determine the number of B cells seeding germinal centres, different authors have used immunohistology of germinal centre sections in conjunction with assuming a binomial distribution of the fractions of two phenotypically distinct B cell populations participating in a given immune response. This approach further assumed that germinal centres are closed to continuous B cell entry. Using such a model, it has been concluded that germinal centres contain two to eight clones, a figure that is usually taken and cited as being essentially correct. The present re-evaluation of those and related experiments lead to an extended mathematical model. This model includes an estimation of errors created by data sampling, two new parameters that take into account possible mistakes in classification of single population GC sections, and the likely variability in the number of seeding B cells. Fitting this new model to experimental data resulted in an estimated mean number of ⟨n⟩ = 23–37 seeder B cells.