B Cell Ontogeny Cells that do not express pre-BCR die by apoptosis Cells expressing pre-BCR undergo "positive selection" Signals via the pre-BCR induce cells to proliferate Surrogate light chain synthesis is shut down Light chain rearrangement starts Further H chain rearrangement is stopped Immature B Cells Light chains pair with m chains(membrane-bound monomeric form) Immature B cells can recognize and respond to foreign Ag, but this interaction results in long-lasting inactivation rather than expansion and differentiation B Cell Ontogeny ◼ Cells that do not express pre-BCR die by apoptosis ◼ Cells expressing pre-BCR undergo “positive selection” ◼ Signals via the pre-BCR induce cells to proliferate ◼ Surrogate light chain synthesis is shut down ◼ Light chain rearrangement starts ◼ Further H chain rearrangement is stopped ◼ Immature B Cells ◼ Light chains pair with m chains (membrane-bound monomeric form) ◼ Immature B cells can recognize and respond to foreign Ag, but this interaction results in long-lasting inactivation rather than expansion and differentiation