A Population Dynamics Model for Clonal Diversity in a Germinal Center

Area of Science:

• Immunology
• Evolutionary Biology
• Computational Biology

Background:

• Germinal centers (GCs) are specialized micro-environments essential for B cell maturation and the development of high-affinity antibodies.
• Within GCs, B cells undergo selection based on antigen and T cell interactions, leading to clonal evolution.
• Recent findings indicate significant variability in GC clonal diversity and selection outcomes, even under identical experimental conditions.

Purpose of the Study:

• To model clonal competition within germinal centers over time.
• To investigate the impact of different selection mechanisms on B cell diversity and evolution.
• To compare model predictions with experimental observations of clonal selection in mice.

Main Methods:

• Development of a birth, death, and mutation model to simulate clonal dynamics in GCs.
• Analysis of stochastic processes underlying diversity loss during clonal competition.
• Study of two distinct selection models: birth-limited and death-limited selection.

Main Results:

• Clonal diversity loss in germinal centers is an inherently stochastic process.
• Death-limited selection preserves diversity and promotes gradual clonal homogenization with increasing affinity.
• Birth-limited selection leads to faster dominance by successful clones.

Conclusions:

• The stochastic nature of evolutionary processes significantly influences germinal center dynamics.
• Selection mechanisms play a critical role in shaping B cell repertoire diversity and affinity maturation.
• The developed model provides a framework for understanding experimental observations of clonal selection in vivo.