Fig 1: The majority of interleukin (IL)-31 expression in polymorphic light eruption (PLE) is by CD11b+ cells. Quantitative analysis of immunohistochemical staining showing the number of (a) interleukin (IL)31+ cells; (b) IL-31 receptor alpha complex (IL31RA)+ cells; and (c) oncostatin M receptor (OSMR)+ cells in different diseases. Visual analysis (a–c) was performed by counting positively stained cells in five of the most densely infiltrated microscopic fields randomly selected from the same section, at a magnification of × 40. (d) Representative images of double staining showing high numbers of CD11b+ cells expressing IL31 in PLE. (e–g) Quantitative analysis showing the number of (e) IL-31-expressing CD11b+, (f) IL31 expressing CD11b+ Siglec8+ (eosinophils); and (g) CD11b+ CD68+ cells (macrophages). Automated analysis for immunofluorescence (e–g) was performed using TissueQuest image analysis software v6·0 (TissueGnostics GmbH, Vienna, Austria). Briefly, nuclei were assessed by 4,6-diamidino-2-phenylindole mean intensity and area measurement, while cell surface and intracellular markers were detected inside and around nuclear staining, respectively. Number of positive cells/mm² was calculated and used for statistical analysis. Data are presented as mean ± SD. P values were determined by Mann–Whitney test. (f) All P values except one [atopic dermatitis (AD) vs PLE] remained significant after Bonferroni correction, setting significance to P = 0·0083; ns, not significant. Scale bar, 50 µm.