Comparative analysis of highly pure cell subsets has the potential to unearth added intricacy in the nature of eQTLs, highlighting that the majority act in a cell specific manner and many eQTLs will likely remain undiscovered if analysis focuses on heterogeneous tissues. This study adds strong evidence to support the concept that a large number of eQTL function in a highly context specific manner in vivo and provide a plausible explanation for a degree of disease susceptibility.