B cells in clinical transplantation tolerance

The rarity of tolerance following clinical transplantation has complicated the study of the responsible mechanisms. Several recent studies of kidney transplant recipients have demonstrated an association between increased numbers of B cells with less mature, inhibitory phenotypes and a state of tolerance. While a growing body of evidence from experimental models supports a role for B cells in regulating or suppressing immune responses, a causative role for B cells in clinical transplantation tolerance has yet to be proven. If B cells are conclusively shown to participate in the development of transplantation tolerance, it will be important to define the responsible mechanisms in order to design monitoring assays and immunosuppressive regimens that favor the development of tolerance.

► Models of autoimmunity, cancer, infection and transplant demonstrate regulatory B cells.
► Tolerance in kidney transplants is associated with increased immature, inhibitory B cells.
► Similar changes in B cell phenotype are not observed in tolerant liver transplant patients.
► B cell depleting agents should be introduced with caution in renal transplantation.