MORPHOMETRIC AND ULTRASTRUCTURAL ANALYSES OF IN VIVO-ACTIVATED MURINELANGERHANS CELLS INDUCED BY ADMINISTRATION OF A STREPTOCOCCAL PREPARATION (OK-432)

Langerhans cells (LCs) are activated in the epidermis by external and internal stimuli, such as antigens and cytokines, respectively. To rev eal the morphologic and functional properties of in vivo-activated LCs during inflammation, we injected the streptococcal preparation OK-432 intradermally into the earskin of mice and performed time-course anal yses by immunofluorescence and electron microscopy, Cellular infiltrat e appeared in the dermis at 6 h after OK-432 injection and had progres sively extended to the dermoepidermal junction at 12 and 24 h, Immunos taining for class II antigen revealed that LCs were enlarged and exten ded long dendrites during inflammation. Acidic compartments such as ly sosomes and multivesicular bodies also increased in number and Golgi a pparatuses developed as demonstrated by electron microscopy and morpho metric analysis. Birbeck granules, although not showing numerical chan ges, were translocated from the Golgi area to the subplasmalemmal area . After epicutaneous application of cationic ferritin, LCs often conta ined endosomes as the result of engulfment by the cytoplasmic projecti ons. The present results indicate that nonspecifically induced dermal inflammation is capable of inducing activation of LCs in vivo, and tha t in vivo-activated LCs have the capacity for active endocytosis and i ntracellular digestion or processing.