We have a technique where we can transfect primary human cells using a plasmid vector construct that contains a fluorescent reporter driven by our promoter sequence insert. The sequence is inserted between the CMV reporter/promoter and MCS. In parallel I aim to transfect primary cells using the original unadulterated vector as a control. Now the question is - will the fluorescent reporter signal in this control be ubiquitous whereas signal from our construct will be specific, or will it be instead that this control will have no signal at all? As these are primary cells, I have no idea whether many of us are casually carrying endogenous (viral?) proteins that will activate the fluorescent reporter via the CMV promoter. Or whether or not I have completely missed the point altogether (i'm new to this).