Recently, pulmonary DC deserved the attention of researchers and clinicians as it was implicated in many diseases
afflicting human lungs. However, there are no available data about the morphological or functional features of
pulmonary dendritic cells in fetal or early neonatal life. The present study aimed to demonstrate the morphological
development of DCs using light-, electron-microscopy, and immunohistochemistry. DCs showed strong
immunoreactivity for both CD8 and CD56. Moreover, DCs strongly expressed CD34, VEGF, NSE, and connexin-43
within the developing pulmonary tissue. By SEM, DCs were polyhedral in shape with short cell processes in fetal
life. By the advancement of the age, DCs became more numerous and exhibited rounded to oval cell bodies with
many fine dendrites. TEM revealed that at early fetal life, DCs were characterized by their heterochromatic
indented nuclei, few cell processes and few organelles. With the advancement of age, DCs showed dendrite-like
processes and displayed signs of high endocytic activities with releasing of secretory materials. At late fetal life,
DCs showed an obvious increase in the nuclear/cytoplasmic ratio and they exhibited a unique connection with
type II pneumocytes and pulmonary endothelium by gap junction. In the early neonate, the DCs cells were seen in
association with T-lymphocytes, neutrophils, telocytes (TCs), and air-blood barrier. They possessed many fine
dendrites, the characteristic Birbeck granules and many vesicles. DCs may contribute to apoptosis, endocytosis,
and angiogenesis. The difference in the maturation status may reflect different roles for DCs in the lung. The
immature DCs may have an antigen-uptake role through endocytosis, while mature DCs may involve in antigen
presentation to T-cells.