**6. Conclusions**

The literature contains ample evidence on cytokines as biomarkers in lung transplantation outcomes. PGD is augmented by IFN-y, IL-6, IL-8, TNF-a, and MCP-1. This could be explained by monocyte involvement and inflammatory changes during ischemia-reperfusion injury. IL-1b, IL-6, IL-10, IL-15, and IFN-γ appear to be strong indicators to supplement the diagnosis of acute rejection in lung transplant recipients. These cytokines are linked to a Th1 immune response associated with acute inflammation. IL-1b, IL-6, IL8, IL-15, IL-17, IFN-γ, and TGF-β are significant contributors to chronic lung allograft dysfunction. IL-12 has also shown to attenuate chronic lung rejection. CLAD appears to be more associated with inflammation and airway neutrophil chemotaxis.

The role of cytokines requires more controlled studies in order for diagnostic characteristics to be attributed. That being said, cytokines and chemokines in primary graft dysfunction, acute rejection, and chronic allograft dysfunction are promising markers of future diagnostic tests and targets of therapies to ultimately improve outcomes and survival in lung transplant recipients.
