Skin Langerhans cells failure to trap bacterial antigen in non-sensitized guinea-pig

We have studied by ultrastructural histo-autoradiography, in a primary immunological response, the behavior of three types of guinea-pig histiocytic cells exposed to 125I-flagellin, lymph node histiocytes, alveolar macrophages and skin Langerhans cells, making use of the experimental model of Nossal et al. (1964). Whereas latero cave lymph node histiocytes exposed to 125I-flagellin by in vivo injection of the labelled antigen into the hind foot of the guinea-pig trap the flagellin as do 20% of alveolar macrophages incubated in vitro in a culture medium containing 125I-flagellin, skin Langerhans cells exposed in vivo (intradermal and hypodermal injection of the antigen) and in vitro, as was done for alveolar macrophages, are never labelled. These results suggest that, despite the fact that it belongs to the mononuclear phagocytic system, the Langerhans cell is not a common essentially phagocytic macrophage but represents a cell lineage involved in more complex immune reactions requiring the cooperation of sensitized lymphocytes.