Histological studies of the lungs of immunized mice with different cytokine gene plasmid treatments. Mice that had been sensitized and repeatedly challenged with nebulized saline (A) or OVA (B-E) were gavaged with non-coding vector, scIL-12, TGF-β, or IL-10 gene plasmids before the challenge phase. The data showed extensive cellular infiltration of the peri- airway region from vector DNA treated mice (B). In contrast, lung tissue from scIL-12 plasmid treated mice (C), TGF-β plasmid treated mice (D), and IL-10 plasmid treated mice (E) showed a much less severe inflammation histologically. Microscopic images were made with an Olympus microscope at a magnification of 100, and images were representative of the experimental group. Paraffin embedded sections were stained with hematoxylin and eosin.