Human mucosal Langerhans cells: postmortem identification of regional variations in oral mucosa

Modified ATPase histochemistry was used to identify and count Langerhans cells (LC) in autopsy tissue from 8 oral mucosal sites, 8-20 h postmortem. The specificity of the ATPase method was confirmed on serial sections with indirect immunofluorescence using monoclonal antibodies OKT6 and antihuman Ia. Average LC counts on ATPase-stained epithelial sheets from each of the 8 sites ranged from 160-550 LC/mm2. Nonkeratinized mucosae of the soft palate, ventral tongue, lip, and floor of the mouth had the highest counts (mean +/- SD, 508 +/- 110 LC/mm2, n = 24), and keratinized mucosae of the hard palate and gingiva had the lowest counts (201 +/- 97 LC/mm2; n = 8). LC frequency was variable in 2 sites: In the dorsal tongue, LC occurred on only one side of filiform papillae and were absent from regularly recurring areas of interpapillary epithelium. In the cheek mucosa, LC clustered around connective tissue papillae and their numbers showed marked individual variation (130-650 LC/mm2). The number of LC in nonkeratinized oral mucosa is approximately the same as in skin, but keratinized oral mucosa has fewer LC. The frequency of oral mucosal LC varies inversely with the degree of keratinization. There are regions of the oral mucosa that have no LC.