Allorecognition by leukocytes of the adaptive immune system

Allorecognition refers to a series of mechanisms by an individual’s immune system distinguishes its own cells and tissue from those of another individual belonging to the same species. This phenomenon is responsible for self-non-self recognition in all multicellular phyla, including invertebrates such as sponges, corals and hydroids. In invertebrates, allorecognition is medaited exclusively by cells of the innate immune system. On the other hand, in addition to innate allorecognition, vertebrates can also distinguish allogeneic cells using leukocytes of the adaptive immune system, which interact with alloantigens using specific receptors (BCR and TCR for B and T lymphocytes, respectively). Such allorecognition leads to an inflammatory immune response, which is response for the rejection of allogeneic cell, tissue and organ transplants. However, in mammalians, a number of regulatory mechanisms have been selected through evolution to suppress deleterious alloimmunity directed to paternal antigens during pregnancy and prevent immune abortion of the fetus by the pregnant female’s immune system. Similar to the fetus, it is now established that certain organs such as the testis and the brain are not prone to inflammation and rejection and referred to as “immune privilege”. Such immunological tolerance involves active processes mediated by regulatory lymphocytes.

In this Research Topic we welcome immunologists experts in the field of allorecognition and transplantation to write reviews recapitulating our current knowledge of the cellular and molecular mechanisms involved in allorecognition by cells of the innate and adaptive immune systems throughout evolution. In addition, we will address the processes by which different subsets of lymphocytes present in mammalians recognize alloantigens and how this influences rejection or tolerance of different allogeneic entities such as the fetus or organ and tissue transplants.