a) Combined quantitative immunohistochemistry data of CD4, CD8 and FOXP3 staining (n=44; 28 progressive, 16 regressive) with total lymphocyte quantification from H&E images (n=112; 68 progressive, 44 regressive) shown. We observe increased lymphocytes (p=0.049) and CD8+ cells (p=0.055) per unit area of epithelium within regressive CIS lesions compared to progressive. Stromal regions adjacent to CIS lesions showed no significant differences in immune cells between progressive and regressive lesions. p-values are calculated using linear mixed effects models to account for samples from the same patient; #p<0.1, *p<0.05. (b-c) Immunohistochemistry images of (b) progressive CIS lesion and (c) regressive CIS lesion with CD4+ T helper cells stained in brown, CD8+ cytotoxic T-cells in red and FOXP3+ T regulatory cells in blue. Immune cells are separately quantified within the CIS lesion and in the surrounding stroma.