Identification of IFN-alpha mRNA in renal tubular epithelial cells of patients affected by lupus nephritis. (A) ß-actin and (B) scramble mRNA expression on seriate sections of patients affected by class IV lupus nephritis, representing the positive and negative controls of the ISH reaction, respectively. (C,D,E). ISH mRNA detection on renal biopsies showed that IFN-alpha mRNA was highly expressed in epithelial cells of proximal tubules in patients with class IV lupus nephritis but it was absent in glomeruli, blood vessels and distal tubules. On the contrary, (F) IFN-alpha mRNA was marginally expressed in class I lupus nephritis. ISH analysis was performed on renal biopsies of four patients for each group, as described on Methods section. ISH, in situ hydridization.