1. CD4+ T cells downregulate Bcl-2 in germinal centers
- Author
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José Vassallo, Georges Delsol, Salvatore Valitutti, Sabina Müller, Florence Capila, Pierre Brousset, Jean-Jacques Fournié, and André Almeida Schenka
- Subjects
CD4-Positive T-Lymphocytes ,CD40 ,Microscopy, Confocal ,biology ,ZAP70 ,Immunology ,Palatine Tonsil ,Germinal center ,Down-Regulation ,CD8-Positive T-Lymphocytes ,Natural killer T cell ,Germinal Center ,Molecular biology ,Lymphocyte Subsets ,Interleukin 21 ,Proto-Oncogene Proteins c-bcl-2 ,biology.protein ,Immunology and Allergy ,Cytotoxic T cell ,Humans ,IL-2 receptor ,Antigen-presenting cell - 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.
- Published
- 2004