Title: Collective dynamics in B cell affinity maturation
Speaker: Ned Wingreen, Princeton University
Abstract: In the humoral immune response, B cells that produce high-affinity antibodies are generated through a Darwinian evolutionary process called affinity maturation. Affinity maturation, which takes place in germinal centers (GC), is driven by cycles of selection (mediated by T cells), division, and hypermutation of B cells. Recently, it was found that the T cells themselves also exhibit dynamic behavior throughout the course of the GC reaction, undergoing affinity-dependent proliferation. A model suggests that this reciprocal stimulation enforces a robust “homeostatic” regulation of the relative number of B cells and T cells in the GC, leading to a constant ratio of GC lymphocytes. But the model also points to a problem: the high mutation rate of GC B cells can lead to “backsliding” of affinity. The proposed solution – a fitness-dependent mutation rate – has been experimentally verified, and has implications beyond B cell affinity maturation.
Zoom: TBA
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