How compartmentalization and proliferation shape the splenic T cell repertoire during an immune response to a complex antigen in mice.

TCR repertoire differences in the spleen during immune responses are mainly driven by compartment size and proliferation, not TCR sequence features, according to a Galton-Watson model.

• Why it matters: Understanding what shapes TCR diversity within lymphoid organs is crucial for insights into immune responses, yet the influence of spatial compartmentalization remains unclear. Clarifying this can improve interpretations of TCR dynamics and immune monitoring.
• What they did: The study analyzed the CDR3β region of TCRs in microdissected splenic compartments from naïve and immunized mice, comparing T cell zones, B cell zones, and germinal centers, and modeled proliferation effects.
• The result: Findings indicate that compartment size and proliferation rates largely explain TCR repertoire differences, suggesting that spatial TCR diversity assessments must consider these factors for accurate interpretation.