MHC class I signaling: new functional perspectives for an old molecule

Donor‐specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody‐mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody‐mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.