PRB4 and infection: These data mimic our microarray results at the protein level, i.e., the increased transcription of the PO pathway genes Pu, Ddc, Bc, yellow-f, yellow-f2, and prophenoloxidase (proPO) activating enzymes (and decreased transcription of a negative regulator of the PO pathway, Spn27a) at the earlier time points is associated with increased PO enzyme activity in Lb17 attacked fly hemolymph 24 h post-infection, when melanotic encapsulation typically occurs [8].