Figure 4

In the adrenal gland (A), strong CAIX immunoreactivity was seen in many cortical cells near the capsule (17W), but the level of expression progressively diminished after birth and, by the end of two years, no CAIX positive cells were seen. In the thymus gland (B), CAIX positive cells were primarily identified near the Hassall's corpuscles (16W) but disappeared by the first year after birth (24M). In the stomach (C), CAIX expression was first seen in surface columnar cells at the 9th week of gestation (9W). At 17 weeks, diffuse immunoreactivity was seen in the glandular and surface columnar cells (17W). This level of expression persisted after birth (24M). In the small intestine CAIX positive cells were restricted to the crypts (D1) and in the large intestine only rare positive cells were identified near the base of the crypts (D2). In the biliary trees, CAIX expression was seen in the epithelium of the entire ductal system and was persistent after birth. The liver (E1) and pancreas (E2) are shown as examples. During early fetal period, extensive CAIX expression was seen in the basal/reserve cells of the respiratory epithelium (F1, 14W) but after birth only rare reserve cells continued to express CAIX (F2, 24M). W = gestational age in weeks; D, M = postnatal age in days and months, respectively. Original magnifications: A1, A2, A3, B1 and C (20×); B2, D1, D2, E1, E2, F1 and F2 (40×).