IMMUNOHISTOCHEMICAL DETECTION OF SIALYL LE(X) ANTIGEN ON MUCOSAL LANGERHANS CELLS OF HUMAN ORAL-MUCOSA FOLLOWING NEURAMINIDASE PRETREATMENT

Histochemical assessment of selected carbohydrate sequences on Langerh ans cells of human oral mucosa was made by combined use of enzyme dige stion and immunostaining with monoclonal antibodies against specific c arbohydrate structures. In both frozen sections and epithelial sheets without the enzyme pretreatment, mucosal Langerhans cells, identified by positive staining with anti-CD1a and HLA-DR antibodies, did not exp ress any carbohydrate antigens on their surface. In contrast, followin g neuraminidase pretreatment of both types of material, the fucosylate d type 2 chain (Le(x)) became detectable on Langerhans cells, indicati ng that sialic acid is the terminal residue of this sequence. Other en zymes were ineffective in this apparent unmasking, and the staining pa tterns of the other related carbohydrate sequences (Le(y), Le(a), Le(b )) remained unaffected by pretreatment with any of the enzymes used. T hese findings suggest that the mucosal Langerhans cells possess a uniq ue carbohydrate chain, the sialyl fucosylated type 2 sequence (sialyl Le(x) antigen).