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Tracing B cell development in human germinal centres by molecular analysis of single cells picked from histological
R Küppers1, M Zhao, M L Hansmann
1Institute for Genetics, University of Cologne, Germany.
Insights
This study reveals that germinal centers are dominated by a few large B cell clones that diversify through somatic hypermutation. Some centers show evidence of late-stage selection, while others may originate from polyclonal activated B cells.
Area of Science:
- Immunology
- Cell Biology
- Genetics
Background:
- Germinal centers are crucial microenvironments for B lymphocyte maturation in lymphoid organs.
- Understanding B cell clonal dynamics within germinal centers is key to immune response comprehension.
Purpose of the Study:
- To investigate the clonal composition and genetic diversity of B cells within human germinal centers.
- To elucidate the processes of somatic hypermutation and selection during B cell development in germinal centers.
Main Methods:
- Micromanipulation of single B cells from human spleen and lymph node germinal centers.
- Amplification and sequencing of rearranged V genes from isolated B cells.
- Analysis of clonal diversity and somatic hypermutation patterns.
Main Results:
- Follicular mantle B cells displayed clonal diversity with germline V gene expression.
- Germinal centers were dominated by a few large B cell clones with intraclonal diversity.
- Evidence of counterselection of replacement mutations in one germinal center suggests a late reaction phase.
- A polyclonal population of activated B cells with unmutated antibodies was identified, potentially representing founder cells.
Conclusions:
- Germinal center B cell populations are shaped by clonal expansion and somatic hypermutation.
- Distinct phases of the germinal center reaction may be identifiable through mutation patterns.
- The origin of germinal centers may involve both selected clones and polyclonal activated B cells.
Abstract:
Germinal centres are areas of intense B lymphocyte proliferation inside primary B cell follicles in spleen and lymph nodes. Rearranged V genes from single human B cells, isolated from histological sections of two such structures by micromanipulation, were amplified and sequenced. Cells from the follicular mantle were clonally diverse and largely expressed germline V genes. Germinal centres were dominated by a few large B cell clones dispersed throughout these structures and exhibiting intraclonal diversity by ongoing somatic hypermutation. Pronounced counterselection of replacement mutations seen in one of the germinal centres may indicate a late phase of the germinal centre reaction. A polyclonal population of activated B cells expressing unmutated antibodies in the dark zone of the other germinal centre may represent the initial founder cells.