Cell alignment in the stratum corneum of frozen sections of specimens of human skin was examined by light microscopy following expansion of the stratum corneum in alkaline buffer. Some degree of ordered structure was found in all specimens examined but considerable variation existed in precision of cell alignment. The typical degree of cell alignment was less precise than that typically observed in experimental animals.

The establishment of a columnar pattern of organization in rat backskin and earskin was examined by using frozen sections expanded in alkaline buffer and by labeling with 3H-TdR and autoradiography. An adult columnar pattern of organization was established earlier in backskin than earskin. In both tissues the appearance of cell columns was related to a decreasing rate of cell proliferation and, for ear, to a decreasing rate of lateral growth of the epidermis.

Alignment of the flattened keratinizing cells of the upper strata of mammalian epidermis leads to the formation of columnar units of structure. In mouse epidermis, mitoses have been found to occur relatively infrequently in the region beneath the center of each cell column where a non-keratinocyte dendritic cell, usually with freatures typical of an epidermal Langerhans cell, is situated. The observed pattern of mitosis could therefore be due either to displacement of central keratinocytes by Langerhans cells or indicate some control of keratinocyte proliferation related either to the Langerhans cells or to the over-lying cell columns. No relationship exists between the position of Langerhans cells and epidermal cell columns in hamster epidermis but measurement of the position of mitosis has shown a reduced frequency of occurrence of mitosis beneath the central region. This pattern of mitosis is therefore unrelated to Langerhans cells and appears to reflect differences in the mitotic potential of basal keratinocytes which could be associated with feedback from the overlying cell columns or with an intrinsic pattern of basal cell activity.