CD4 and neoplasm: By measuring second-harmonic generation (SHG), we observed no change in collagen fibre alignment and CD8+ T cell content between tumours from Col IWT and Col Ir/r pancreata or between parental and DDR1KD tumours, although CD45-, F4/80- or CD4-expressing cells were reduced in tumours from Col Ir/r pancreata (Extended Data Fig. 9b,c).