I found this review very interesting with the ATP, ADP and AMP recycling plus immunology background. Zhao H, Bo C, Kang Y and Li H (2017) What Else Can CD39 Tell Us? Front. Immunol. 8:727. doi: 10.3389/fimmu.2017.00727 Abstract: As the rate-limiting enzyme in ATP/ADP–AMP–adenosine pathway, CD39 would be a novel checkpoint inhibitor target in preventing adenosine-triggered immune-suppressive effect. In addition, CD39hi Tregs, but not CD25hi Tregs, exhibit sustained Foxp3 levels and functional abilities, indicating it could represent a new specific marker of Tregs. Similarly, inhibition of CD39 enzymatic function at the surface of tumor cells alleviates their immunosuppressive activity. Far from conclusive, present research revealed that CD39 also dephosphorylated and thus inactivated self- and pathogen-associated phosphoantigens of Vγ9Vδ2 T cells, which may be the most promising subpopulation for cellular vaccine. CD39 is also tightly related to Th17 cells and can be regarded as a Th17 cells marker. In this review, we focus on present research of CD39 ectoenzyme and provide insights into its clinical application. Keywords: CD39, extracellular ATP, adenosine, Tregs, γδ T cell, CD161, Th17 cell, Bregs I felt it gave a good feel about the level of complexity and hence help me understand the time spans usually involved. I particularly liked their line "The reasons for this negligence were majorly due to technical and conceptual difficulties in our understanding"