Studies on Langerhans cells in the tracheal squamous metaplasia of vitamin A deficient rats.

LCs in the tracheal squamous metaplasia of vitamin A deficient rats were studied. The first appearance of LCs with Birbeck granules (BGs) was in the stage of stratification. The number of LCs increased along with the development of metaplasia, but decreased in number in the later stage, where basal cells also differentiate into flattened epithelium. In the area where only basal cells differentiated into flatter epithelium, without a cornified layer, LCs with BGs could also be found. These findings suggest that LCs which originate in bone marrow mature in squamous epithelium. The distribution and morphology of LCs are dependent on the state of keratinocytes, but not the presence of a cornified layer.