June 2013 A tool for the conditional deletion of the transcriptional repressor Bcl6


A tool for the conditional deletion of the transcriptional repressor Bcl6

B6.Cg-Bcl6/Rbrc RBRC05663


Courtesy of Toshitada Takemori, M.D., Ph.D., RIKEN Center for Integrative Medical Sciences

Histological distribution of IgG1+ memory B cells in the spleens of conditional Bcl6-deficient (Bcl6f/f x mb-1-cre+/-; c and d) and control (Bcl6+/+ x mb-1-cre+/-; a and b) mice by confocal microscopic analysis. IgG1+ cells (green) within the B220+ follicles (blue) were identified from the images, and their expression of peanut agglutinin (PNA, yellow) was determined. IgG1+ cells of the B220+PNA-phenotype (memory cells) were located within the B cell follicles at day 7 after immunization in mutant (c and d) and control (a and b) mice. IgG1+ cells of the plasma cell phenotype were confined largely to the extrafollicular areas (data not shown).


Memory B cells are long-lived quiescent B cells selected for their expression of somatically mutated, high-affinity antibodies in the T cell-dependent germinal center (GC) reaction. This reaction is accompanied by the up-regulation of the transcriptional repressor B cell leukemia/lymphoma 6 (Bcl6), on which GC B cell differentiation depends. A puzzling observation has been that the memory B cell compartment also contains cells expressing unmutated, low-affinity antibodies. To obtain a comprehensive understanding of the population dynamics underlying GC-dependent and -independent memory B cell development, Takemori and colleagues established a mutant mouse strain carrying aloxP-flanked Bcl6 exons 7-9 allele, with these exons encoding the Bcl6 zinc finger domains ZF1 to ZF5. Using conditional Bcl6 ablation, they demonstrated that the unmutated memory cells are generated through proliferative expansion early after immunization in a T cell-dependent, GC-independent manner. GC-independent memory B cells are joined later by their somatically mutated GC descendants, and both types of memory cells efficiently generate an adoptive secondary antibody response [1].


Depositor : Toshitada Takemori, M.D., Ph.D.
RIKEN Center for Integrative Medical Sciences 
Reference : [1]  Kaji T, Ishige A, Hikida M, Taka J, Hijikata A, Kubo M, Nagashima T, Takahashi Y, Kurosaki T, Okada M, Ohara O, Rajewsky K, Takemori T. Distinct cellular pathways select germline-encoded and somatically mutated antibodies into immunological memory. J. Exp. Med.; 209(11):2079-97, 2012.



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