MORPHOLOGICAL AND QUANTITATIVE-ANALYSES OF NORMAL EPIDERMAL LANGERHANS CELLS USING CONFOCAL SCANNING LASER MICROSCOPY

Confocal scanning laser microscopy (CSLM), when used in conjunction wi th computerized image processing systems, provides a powerful tool for morphological and quantitative analyses of biological tissues. In thi s study, normal human epidermal sheets were stained by an indirect imm unofluorescence method using anti-CD1a monoclonal antibody. positively stained epidermal Langerhans cells (LCs) were visualized using the Bi o-Rad MRC-600 Confocal Imaging System. Images obtained from the confoc al microscope were volumetrically rendered and quantitatively analysed using ANALYZE(TM) (Version 4.0) running on a Sun SPARC 2 Workstation, Normal epidermal LCs were shown to be large disc-like structures with five to nine long dendritic processes per cell, orientated with their flat surfaces parallel to the skin surface. LCs form a monolayer netw ork of cells distributed evenly throughout the suprabasal layers of th e epidermis, with no direct physical contact between dendritic process es. Mean LC density was estimated to be 582 per mm(2) (95% confidence intervals, CI = 233-940), and mean cell volume was 612 mu m(3) (95% CI = 257-1020). LCs in sun-exposed sites were significantly lower in mea n cell density, but larger in mean cell volume, than in covered sites. Mean surface area projected by LCs was estimated to be 26.8% (95% CI = 18.9-34.2), and this value did not show significant regional or indi vidual variation. Our data support the notion that epidermal LCs are o rganized in such a way as to maximize their surface area for efficient trapping of antigens, and a reduction in LC density per unit area in sun-exposed sites is compensated for by an increase in the mean cell v olume.