Recall that B-cells from neonatal spleen and adult marrow are susceptible to tolerance induction via deletion or editing strategies we discussed in class. However, if only early B-cell differentiation stages are susceptible to tolerance induction, consider this potential problem: Memory responses and long-lived plasma cells contain somatically mutated antibodies, that were selected for higher affinity. These mutations occur during primary responses, yielding altered CDR's. Since the mutations occur in functionally "mature" B-cells, how is any autoreactivity generated by these mutations eliminated from the memory B-cell pool?

Outline an experiment to establish whether mature B-cells that are the immediate progenitors of memory cells transit a "second window" of tolerance susceptibility while undergoing somatic mutation during initial antigen challenge. Be sure to indicate:

• how you would identify/isolate arising memory clones or their progenitors;

• how you would assess tolerance susceptibility and/or induction

• what your control and comparison groups would be.
• Describe the result you would expect it there is such a second window of tolerance susceptibility.