Foxp3 is a transcript factor for regulatory T cell development. Interestingly, Foxp3-expressing cells were identified in B cells, especially in CD19(+)CD5(+) B cells, while those were not examined in CD19(+)CD5(-) B cells. Foxp3-expressing CD5(+) B cells in this study were identified in human PBMCs and were found to consist of 8.5+/-3.5% of CD19(+)CD5(+) B cells. CD19(+)CD5(+)Foxp3(+) B cells showed spontaneous apoptosis. Rare CD19(+)CD5(+) Foxp3(+) regulatory B cell (Breg) population was unveiled in human peripheral blood mononuclear cells and suggested as possible regulatory B cells (Breg) as regulatory T cells (Treg). The immunologic and the clinical relevant of Breg needs to be further investigated.
Apoptosis ; B-Lymphocytes ; B-Lymphocytes, Regulatory ; Humans ; T-Lymphocytes, Regulatory

IL-10 production by CD19(+)CD5(+) B cells was investigated, by determining the expression levels of CD19, a classical B cell marker. Peripheral mononuclear cells were stained with fluorescence-conjugated anti-CD5, anti-CD19, anti-IL-10, and Annexin V. Interestingly, IL-10-producing B cells were found to be localised within the CD19(low)CD5(+) B cell subset. Apoptotic changes were also observed mainly in CD19(low) cells among B cells. Thus, CD5(+) B cells should be classified as CD19(high) and CD19(low) cells, and the immunological significance of CD19 for the IL-10 production by CD5(+) B cells requires further studies.
Antigens, CD19/metabolism ; Antigens, CD5/metabolism ; Apoptosis/immunology ; B-Lymphocyte Subsets/cytology/*immunology ; Cell Separation ; Flow Cytometry ; Humans ; Interleukin-10/*biosynthesis