In order to investigate the morphological characteristics of dendritic cells in the mammary gland, the appearance on the clear cells(CLs) or ATPase-positive dendritic cells(APDCs) have been observed by the light microscope. CLs were observed in the mammary tissues of the experimental animals, such as mice, rats, guinea pigs, rabbits, cats, dogs, pigs, cows and Korean native goats, and these CLs were confirmed as the ATPase-positive cells of typical dendritic appearance(APDCs). The APDCs were distributed in between the secretory epithelial cells, between the secretory epithelial cells and the myoepithelial cells, the basal area of the secretory epithelial cells, the interalveolar and interlobular connective tissues, and in between the epithelial cells of secretory duct. The APDCs were observed more frequently during the middle period of lactation than the other periods, and were irregularly or uniformly distributed according to the location. The mean difference between the inbred and the noninbred counts in the mice was statistically significant(P0.0001), and the similar result was presented in the rats(P0.0000)

In order to investigate the morphological characteristics of dendritic cells in the mammary gland of the mouse (C57 BL/6), rat (W), rabbit and cat, the fine structures of the dendritic cells have been observed by the electron microscope. The dendritic cells with the well-developed processes had an irregular shape, and lacked the desmosome. The pinocytotic vesicles and tubular invaginations of the cell membrane were frequently observed, and the mitochondria with the well-developed cristae were located in the restricted region in the cytoplasm of the dendritic cells. The nuclei of dendritic cells were indented. In the mice and rats, the dendritic cells had a few langerhans cell granules (Birbeck granules). From the above results, it is confirmed that the ATPase-positive dendritic cells in the mammary gland are the langerhans cells