The role of B cell immunity in VCA graft rejection and acceptance

Vascularized composite allotransplantation (VCA) has emerged as the most recent field of transplantation to offer an alternative treatment for those patients that have failed or are not suitable candidates for conventional therapy. Most of the current clinical experience in this field is with recipients of skin containing grafts such as the face, upper extremity and abdominal wall transplants. Like solid organ recipients, VCA recipients require lifelong systematic immunosuppression to maintain their grafts. To date, the most successful immunosuppressant regimens are calcineurin inhibitor based and have been targeted to the control of T cells. While these regimens have resulted in excellent short term graft survival in solid organ transplantation, achieving significant improvements in long term survival has been more challenging. The reasons are multi-factorial, but a role for B cells and humoral immunity has been proposed. Antibody mediated rejection leading to chronic rejection has been cited as the leading cause of renal graft loss. While the number of VCA transplants performed is still small, evidence to date suggests that antibody mediated rejection may occur less frequently than seen in solid organ transplants. Here we will discuss the role of B cell immunity in solid organ transplantation as it pertains and contrasts to the field of VCA and present some examples of possible sequela of B cell immunity in a series of hand transplant recipients.