Reduction in Number and Morphologic Alterations of Langerhans Cells After UVB RadiationIn Vivo are Accompanied by an Influx of Monocytoid Cells into the Epidermis  Stefano Bacci, Paolo Romagnoli, J. Wayne Streilein  Journal of Investigative Dermatology  Volume 111, Issue 6, Pages 1134-1139 (December 1998) DOI: 10.1046/j.1523-1747.1998.00406.x Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Effects of UVB radiation on the number of Langerhans cells per mm2 of epidermis.▪, Untreated controlsin vivo;●, untreated controlsin vitro;□, UVB irradiatedin vivo;^, UVB irradiatedin vitro. Mean values and SEM are indicated, the number of sample units was three (n = 3) per experimental condition and time point, evaluated by fluorescence microscopy. Details on statistics are given inMaterials and Methods. The number of Langerhans cells decreased significantly 2 h after treatmentin vivo (p < 0.001versus untreated controls) and recovered within 24 h. On the contrary, treatment with UVBin vitro led to a long-lasting reduction in the number of Langerhans cells per mm2 and the differencesversus untreated,in vitro controls was significant 24 h after irradiation (p < 0.05). As a consequence, the difference between 2 and 24 h after irradiation was significantin vivo (p < 0.001), but notin vitro. Journal of Investigative Dermatology 1998 111, 1134-1139DOI: (10.1046/j.1523-1747.1998.00406.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Morphologic effects of UVB radiation on Langerhans cells,in vivo andin vitro. Inin vivo experiments, as compared with untreated controls (a), Langerhans cells had fewer and less branched dendrites 2 h after irradiation (b). These effects were reversed in part at the end of the experiment, 24 h after irradiation (c). Similar findings were obtainedin vitro (d, untreated control;e, 2 h after irradiation), but in this case there was no recovery at the end of the experiment. Indirect immunofluorescence for Ia. Laser scanning microscopy (a–c) and conventional fluorescence microscopy (d, e);scale bar, 40 μm. Journal of Investigative Dermatology 1998 111, 1134-1139DOI: (10.1046/j.1523-1747.1998.00406.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 Effects of UVB radiation on the number of epidermal dendritic cells per 100 basal keratinocytes.□, Unirradiated controls; o, mice 2 h after UVB. Mean values and SEM are indicated, based on three mice per experimental point (n = 3), evaluated by electron microscopy. The numbers of dendritic cells upon irradiation were significantly different betweenin vivo andin vitro experiments (p < 0.05). In the former condition, the number of epidermal dendritic cells increased upon irradiation, whereas it decreased in the latter condition. Journal of Investigative Dermatology 1998 111, 1134-1139DOI: (10.1046/j.1523-1747.1998.00406.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Effects of UVB radiation on the number of dendrite profiles per epidermal dendritic cell body.□, Unirradiated controls; o, UVB-irradiated mice. Mean values and SEM are indicated, based on three mice per experimental point (n = 3), evaluated by electron microscopy. The number of dendrite profiles per dendritic cell decreased significantly (p < 0.05) bothin vivo andin vitro. Journal of Investigative Dermatology 1998 111, 1134-1139DOI: (10.1046/j.1523-1747.1998.00406.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Morphologic effects of UVB radiation on epidermal dendritic cells, analyzed by electron microscopy. (a) Cell from control mouse skin, with many smooth vesicles and one small Birbeck granule, i.e., the marker of Langerhans cells (arrow). Electron microscopy;scale bar, 0.75 μm. (b) Cell from mouse skin 2 h after UVB radiationin vitro. The cytoplasm contains many, dilated vesicles and some Birbeck granules, i.e., the markers of Langerhans cells (arrows). Vacuolization of keratinocytes (asterisk) was more frequent than afterin vivo irradiation. Electron microscopy;scale bar, 0.5 μm. (c) Cell from mouse skin 2 h after UVB radiationin vivo. The cytoplasm is almost devoid of organelles and inclusions; thearrowhead points to a primary lysosome. Keratinocytes appear in general to be well preserved in these experimental conditions, but some contained a huge, translucent, smooth membrane bound vacuole (asterisk). Electron microscopy;scale bar, 1.5 μm. Journal of Investigative Dermatology 1998 111, 1134-1139DOI: (10.1046/j.1523-1747.1998.00406.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions