has plasma membrane part capable of mature B cell regulatory B cell Regulatory B cells reportedly represent 1-2% of the spleen and 7-8% of the peritoneal B220-positive cells in mice. They are also found in the bone marrow, lymph node, and blood of mice. These cells are also reportedly capable of secreting IL-10 and are reportedly CD5-positive, CD21-positive, CD24-positive, CD93-negative, B220-positive, IgM-positive, and IgD-positive. interleukin-10 production negative regulation of immune response membrane-spanning 4-domains subfamily A member 1 antigen-presenting glycoprotein CD1d