Flow cytometric analysis showed that relative amounts of Lag antigens in LC increased during the second trimester and that fetal LC of 18 weeks EGA expressed the same amounts of HLA-DR, CD1a, and Lag antigens as did adult human LC. The Lag + cells until 17 weeks EGA showed a variety of staining intensities and immunoelectron microscopy revealed that they contained various amounts of Lag-reactive BG. In the second trimester, CD1a + cells and Lag + cells were also identified in the epidermis, although Lag + cells appeared later than CD1a + cells. Epidermal LC of palms and soles reached a peak in number in the first trimester but were rarely detected after 18 weeks estimated gestation age (EGA), whereas, in other regions, their number increased with age.
In the second trimester, regional variations in LC development were observed. Some of the former co-expressed HLA-DR antigens but not CD 1a antigens. In the first trimester, CD36 + dendritic epidermal cells were identified before the appearance of CD 1a + cells and Lag + cells. Samples were obtained from multiple anatomic sites and stained with anti-CD36, anti-CD 1a, and anti-HLA-DR antibody as well as Lag antibody specifically reactive to BG and some vacuoles of human LC. The regional development of Langerhans cells (LC) and the formation of Birbeck granules (BG) were examined in human embryonic and fetal skin.
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