Human B1 cells consist of CD20+CD27+CD43+CD70− cells bearing a skewed B cell receptor repertoire, and are present in umbilical cord and adult peripheral blood.

No abstract

The traditional definition of natural antibodies (NAbs) states that these antibodies are present prior to the body encountering cognate antigen, providing a first line of defense against infection thereby, allowing time for a specific antibody response to be mounted. The literature has a seemingly common definition of NAbs; however, as our knowledge of antibodies and B cells is refined, re-evaluation of the common definition of Nabs may be required. Defining Nabs becomes important as the function of NAb production is used to define B cell subsets (1) and as these important molecules are shown to play numerous roles in the immune system (Figure 1). Herein, we aim to briefly summarize our current knowledge of NAbs in the context of initiating a discussion within the field of how such an important and multifaceted group of molecules should be defined.

B-1cells play critical roles in defending against microbial invasion and in housekeeping removal of cellular debris. B-1cells secrete natural antibody and manifest functions that influence T cell expansion and differentiation and in these and other ways differ from conventional B-2 cells. B-1-cells were originally studied in mice where they are easily distinguished from B-2cells, but their identity in the human system remained poorly defined for many years. Recently, functional criteria for human B-1cells were established on the basis of murine findings, and reverse engineering resulted in identification of the phenotypic profile, CD20+CD27+CD43+CD70−, for B-1cells found in both umbilical cord blood and adult peripheral blood. Human B-1cells may contribute to multiple disease states through production of autoantibody and stimulation/modulation of T cell activity. Human B-1cells could be a rich source of antibodies useful in treating diseases present in elderly populations where natural antibody protection may have eroded. Manipulation of human B-1cell numbers and/or activity may be a new avenue for altering T cell function and treating immune dyscrasias.