Dysfunctional immunoglobulins (Igs) that are prone to aggregation are unavo
idably generated by the diverse repertoire of B cells. Here, Fred Stevens a
nd Yair Argon analyse the patterns of mutations that lead to pathological I
gs, account for non-random mutations in human Ig sequences and suggest the
exertion of selective forces, which contribute to determining and limiting
the Ig repertoire.