IL-10 is Predominantly Produced by CD19(low)CD5(+) Regulatory B Cell Subpopulation: Characterisation of CD19 (high) and CD19(low) Subpopulations of CD5(+) B cells

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.