Global changes in transcript abundance have also been measured in the blood of patients with infectious diseases. In this context, alterations of blood transcriptional profi les are a refl ection of the immunological response mounted by the host against pathogens. Th is response is initiated by specialized receptors expressed at the surface of host cells recognizing pathogen-associated molecular patterns [71] . Diff erent classes of pathogens signal through diff erent combinations of receptors, eliciting in turn diff erent types of immune responses [72] . Th is translates experimentally into distinct transcriptional programs being induced upon exposure of immune cells in vitro to distinct classes of infectious agents [73] [74] [75] . Similarly, patterns of transcript abundance measured in the blood of patients with infections caused by diff erent etiological agents were found to be distinct [13] .