CD27 and bacterial infectious disease: Different Breg phenotypes have been identified and studied in association with different diseases, such as CD19 + CD24highCD27+, CD19+IgM + CD27+ and CD19 + CD1dhighCD5+ in autoimmune diseases [12–14], CD19 + CD38 + CD1d + IgM + CD147+ and CD24highCD27+ in cancer [15–17], CD19 + CD38+ and CD19 + CD24highCD38high in viral and bacterial diseases [9, 18, 19], CD19 + CD1d + CD5+, CD19 + IgM + IgD+ and CD19 + CD5 + IL10+ in parasitic diseases [20–22], and CD19 + CD24highCD38high, CD19 + IL10+ and CD19 + IgM + CD27+ in transplant recipients [12, 23–25].