Transplant Tolerance: New Insights and Strategies for Long-Term Allograft Acceptance

Figure 1

Mechanisms of alloantigen recognition. In direct presentation, donor APCs are able to present alloantigens to alloreactive T cells from the recipient. In indirect presentation, alloantigens are taken up from donor cells by recipient DCs that process and present alloantigens to alloreactive T cells. In semidirect presentation, intact MHC molecules are transferred to recipient DCs that directly present alloantigens through donor-MHC or process and present alloantigens as described for indirect presentation.