Corrigendum to “The Role of Costimulation Blockade in Solid Organ and Islet Xenotransplantation”

Costimulation pathways in T cell regulation. Upon MHC-antigen interaction with the TCR, costimulation pathways can augment or suppress the activation of the T cell. From left to right, CD28 is activated by CD80/CD86. CTLA-4 coinhibitor competes with CD28 for binding to CD80/CD86. CTLA-4Ig and belatacept work by taking advantage of their higher affinity to CD28 over CD80/CD86 and thereby block CD80/CD86 activation of CD28. CD154 and CD40 are other potent activators of T cells; monoclonal antibodies against either of these surface proteins have potential for application in transplant immunosuppression. PD-1 is expressed on T cells, and interaction with PD-1 ligand (PD-L1) produces a suppressive signal to the T cell.