Increased sub-epithelial collagen deposition in the airways of ovalbumin sensitised and challenged mice. MSB staining of representative airways from each treatment group at 12 days after final challenge. (A) saline sensitisation/saline challenge (B) saline sensitisation/ovalbumin challenge (C) ovalbumin sensitisation/saline challenge (D) ovalbumin sensitisation/ovalbumin challenge. Increased blue-staining sub-epithelial collagen is seen in the ovalbumin sensitised/challenged airway compared with the three controls, which have similar appearances. Scale bar represents 50 μm.