HLA system in solid organ transplantation part 9

It has been hypothesized that the balance or interplay between the effector  and the regulatory T cells can determine the ultimate outcome of the alloresponse and the fate of the transplant, which could be potentially be modified by the strength of the alloactivation caused by the number, antigen density and relative immunogenicity of foreign MHC molecules. In addition, the innate defence system has also been shown  to play an important role in this respect. The innate defence system is primed to full force  in the process of organ transplantation, owing to the  cytokine release accompanying the injury to the  transplanted organ related to organ harvesting, storage damage and ischemia-reperfusion injury; which can be more pronounced  when using organs from brain death donors (associated with a cytokine storm) and after prolonged cold ischemia times following donation after cardiac death. The activation of the  innate system leads to the release of powerful inflammatory cytokines and other inflammatory mediators like oxygen reactive species and complement molecules, as well  as the expression of damage-associated molecular patterns; all of them important co-adjuvants for the activation of dendritic cells and other antigen-presenting cells, and eventually T and B cells.