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|Type:||Artigo de periódico|
|Title:||Cd4+ T Cells Downregulate Bcl-2 In Germinal Centers|
|Abstract:||Germinal centers (GCs) are the main site of T cell-dependent antibody responses. Upon antigen challenge, GCs comprise mostly B cells undergoing proliferation, somatic hypermutation and antigen-affinity selection. GC B cells down-modulate the expression of Bcl-2 protein and are highly sensitive to apoptosis to eliminate autoreactive or low-affinity cells. Bcl-2 is still expressed in a few GC cells, whose identity remains unclear. To address this issue, we examined by confocal microscopy the expression of Bcl-2 by different GC lymphocyte subsets in hyperplastic tonsils. We found that the vast majority of Bcl-2+ GC cells are T lymphocytes. Conversely, while in the mantle zone and in the interfollicular areas T cells are almost exclusively Bcl-2 +, in the GC, most T lymphocytes are Bcl-2-. In addition, most of the CD4+ GC T cells are Bcl-2-, while nearly 100% of the CD8+ GC T cells are Bcl-2+. The Bcl-2 downregulation by both B and CD4+ T GC cells supports the concept that these two subsets may undergo a selection process in this microenvironment. © 2005 Springer Science+Business Media, Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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