... ultimately developing into alveoli from week 36 onward Claudin- 3, -4 and -7, but not claudin- 1 and -5, were positive in type II pneumocytes (Fig 3A-3G, 4A-4G) Claudin- 1, -3, -4 and -7 were expressed ... Immunoreactivity scores for claudin- 1, -3, -4, -5 and- 7 in different types of pulmonary cells in developing human lung during various gestational periods Claudin type Pseudo-glandular period day 52-week 16 ... positive in all epithelial cell-lining airways, but claudin- 1 was positive mainly in large bronchi and its expression was usually quite weak Claudin- 3, -4, -5 and -7 were positive and claudin- 1 negative...