Guinea Pig Skin Research Articles

Relationship between the skin permeation movement of propranolol and skin inflammatory reactions.

We studied inflammatory reactions induced by dermal application of the beta-blocker propranolol (PRL) in ethanol to guinea pigs in order to elucidate the relation of the reactions with the cumulative PRL permeating amount through the stratum corneum or the PRL content in the stripped skin, and to investigate the chemical mediators responsible for the reactions. The cumulative PRL permeating amount through the stratum corneum increased rapidly up to 2 h after dermal application, then increased linearly with time up to 24 h after application. Visual observation revealed formation of erythema and edema at the applied site of PRL, and histopathological examination revealed infiltration of pseudoeosinophiles of dermis and epidermis and degeneration/necrosis of epidermis. In general, it was considered that the duration and the extent of these reactions were dependent on the PRL dosage and application time. It was expected that the cumulative PRL permeating amount through the stratum corneum could be used to predict possible inflammatory reactions during development of transdermal drug delivery systems. On the other hand, contact of PRL with guinea pig skin tissues released histamine, and intradermal injection of PRL caused an increase of capillary permeability at the site of application. Also, the inhibitory effects of anti-inflammatory agents (diphenhydramine, dexamethasone, indomethacin, cyproheptadine hydrochloride, CV3988 and AA-861) to PRL-induced erythema formation demonstrated that histamine and prostaglandins were responsible for the inflammatory reactions induced by PRL.

Potent induction of a neutrophil and eosinophil-rich infiltrate in vivo by human mast cell tryptase: selective enhancement of eosinophil recruitment by histamine.

Tryptase is the most abundant protein constituent of the secretory granules of human mast cells, but little is known of the contribution of this serine proteinase in acute allergic reactions. We have purified tryptase from human lung tissue by immunoaffinity procedures, and have investigated its potential to provoke an inflammatory infiltrate in vivo. Within 6 h of injection into the skin of guinea pigs, the accumulation of large numbers of neutrophils and eosinophils was observed, and those eosinophils closest to the injection site were partially degranulated. Similarly, injection of tryptase into the peritoneum of mice, even in quantities as low as 5 ng, stimulated the ingress of neutrophils. The response was dose dependent at 3, 6, and 16 h, with increases in median numbers of up to 400-fold. At the later time points eosinophil numbers were increased by up to 10-fold, and there were elevations also in the numbers of lymphocytes and macrophages. In both models, the actions of tryptase appeared to be dependent on an intact catalytic site. Coinjection of heparin with tryptase had relatively little effect on tryptase-induced responses. On the other hand, although histamine did not itself stimulate cell accumulation, over a range of concentrations it altered the cellular composition of the infiltrate induced by tryptase. Addition of histamine to tryptase provoked selective increases in eosinophil numbers of up to fivefold in the mouse peritoneum. Tryptase may provide an important stimulus for granulocyte recruitment in allergic disease.

Production of Murine Monoclonal Antibodies to Guinea Pig Leukocytes and Immunohistochemistry of Guinea Pig Skin Exposed toSchistosoma mansoni

Using histochemical ATPase-staining of the guinea pig epidermal sheet, we have demonstrated remarkable accumulations of ATPase-positive cells after exposure to attenuated Schistosoma mansoni cercariae. To characterize further the cells accumulating in the skin after exposure to S. mansoni, we produced a panel of monoclonal antibodies (MAb) to guinea pig leukocytes. These were immunohistochemically classified into 15 types and included MAb to the major histocompatibility complex (MHC) Class I and Class II molecules, shared antigens of all lymph node cells or between lymph node cells and Langerhans' cells (LC), T cells and macrophages (M phi), and M phi including the large Tingible body M phi in the secondary follicle. Varied MAb to M phi, including commercially available MAb (MR-1), were negative with ATPase- and MHC Class II-positive cells accumulated in the skin exposed to S. mansoni. Three MAb (HUSM-30 and 46, and commercially available MSgp2) detected an identical staining profile of accumulated cells with epidermal LC, but two MAb (HUSM-12 and 42) positively stained accumulated cells but not resident LC. These results indicate that the cells accumulated in the guinea pig skin within a few days after exposure to attenuated cercariae of S. mansoni are closest to LC, not to Mø, and may be blood-borne LC/dendritic cells.

Reverse iontophoresis: monitoring prostaglandin E2 associated with cutaneous inflammation in vivo.

In response to topical application of irritants, increased concentrations of prostaglandin E2 (PGE2) are found in human skin exudate and in cultured dermal fibroblasts. In this study, PGE2 generated in response to transdermal delivery of irritant drug compounds was monitored in hairless guinea pig (HGP) by a non-invasive method, reverse iontophoresis. Reverse iontophoresis is the movement of molecules from the skin under the influence of an applied electric field. Irritant drug compounds were applied with iontophoresis (electrotransport), and reverse iontophoresis of PGE2 from skin was monitored by radioimmunoassay (RIA) after extraction from the delivery system. Chlorpromazine was used as a model drug irritant. When chlorpromazine and saline were applied over a range of current densities from 0 to 200 microA/cm2, visual scores of erythema and edema yielded a correlation with measured skin efflux of PGE2 (r = 0.86). Delivery of chlorpromazine resulted in greater efflux of PGE2 than delivery of non-irritant saline controls under the same delivery conditions. Five drug compounds, chloroquine, promazine, chlorpromazine, tetracaine, metoclopramide, and saline were applied to hairless guinea pig skin. The 6 agents were similarly rank ordered by visual erythema/edema scores and by PGE2 efflux, indicating that the quantity of PGE2 effluxed reflects the intensity of skin irritation. In contrast, vasoconstriction or vasodilation produced by the local delivery of vasoactive agents did not correlate with PGE2 skin efflux, indicating that this measurement is specific for an inflammatory response. In summary, PGE2 generated in response to transdermally applied drug irritants can be monitored non-invasively in vivo by reverse iontophoresis.

Reinterpretation of endothelial cell gaps induced by vasoactive mediators in guinea-pig, mouse and rat: many are transcellular pores.

1. In response to vascular permeabilizing agents, particulates circulating in the blood extravasate from venules through endothelial cell openings. These openings have been thought to be intercellular gaps though recently this view has been challenged. 2. To define the precise location of endothelial cell gaps, serial section electron microscopy and three-dimensional reconstructions were performed in skin and cremaster muscle of guinea-pigs, mice and rats injected locally with agents that enhance microvascular permeability: vascular permeability factor, histamine or serotonin. Ferritin and colloidal carbon were injected intravenously as soluble and particulate macromolecular tracers, respectively. 3. Both tracers extravasated from venules in response to all three permeability enhancing agents. The soluble plasma protein ferritin extravasated primarily by way of vesiculo-vacuolar organelles (VVOs), interconnected clusters of vesicles and vacuoles that traverse venular endothelium. In contrast, exogenous particulates (colloidal carbon) and endogenous particulates (erythrocytes, platelets) extravasated from plasma through transendothelial openings. 4. Serial electron microscopic sections and three-dimensional reconstructions demonstrated that eighty-nine of ninety-two openings were transendothelial pores, not intercellular gaps. Pore frequency increased 3- to 33-fold when carbon was used as tracer. 5. The results demonstrate that soluble and particulate tracers extravasate from venules by apparently different transcellular pathways in response to vasoactive mediators. However, some pores may derive from rearrangements of VVOs.

Enhanced Serine Protease Activities in the Sulfur Mustard-Exposed Homogenates of Hairless Guinea Pig Skin

Skin homogenates of hairless guinea pigs exposed percutaneously to sulfur mustard (SM) were investigated by measuring four serine protease activities (elastase, tryptase, chymase, and Asp-ase) using sensitive chromogenic substrates. The homogenate samples from skin area directly exposed to S M showed enhanced elastase activities. The tryptase (trypsin-like enzyme) activity also increased slightly; however, the chymase (chymotrypsin-like enzyme) and Aspase (cleave after aspartic acid) activities did not show any increase. The enhanced elastase activities after SM exposure indicate that inflammation is present in the SM lesions. The inhibitory potency of MeO-Suc-Ala-Ala-Pro-Val-CH2Cl (an elastase inhibitor) and two amidine derivatives (inhibitors of trypsin-like enzyme) was tested against the activities present in samples from both exposed and control tissues. The elastase inhibitor decreased the hydrolysis of elastase substrate in the samples from SM-exposed skin to a greater extent than the samples from control tissues. The two trypsin inhibitors decreased the activity in samples from exposed and control tissues equally well. These substrate and inhibitor studies facilitate the characterization of various proteases affected by SM and may be useful for elucidating the mechanism of SM-induced vesication.

Detection of programmed cell death in anagen hair follicles of guinea pig skin by labeling of nick ends of fragmented DNA.

Detection of programmed cell death in anagen hair follicles of guinea pig skin by labeling of nick ends of fragmented DNA.

Skin absorption of the industrial catalyst dimethylethylamine in vitro in guinea pig and human skin, and of gaseous dimethylethylamine in human volunteers.

The aims of the study were three-fold: to assess the skin uptake of the industrial catalyst dimethylethylamine (DMEA) (a) in vitro from water solutions by fresh guinea-pig and human skin specimens, (b) in gaseous form in vivo in human volunteers, and (c) to estimate the relevance of the uptake as an occupational hazard. Specimens from the in vitro and in vivo experiments were analysed by gas chromatography using a nitrogen-sensitive detector. DMEA, diluted with water or isotonic saline solution was applied to fresh human or guinea-pig skin, mounted in Teflon flow-through cells with a perfusion fluid flow rate of 1.5 ml/h, samples being collected at 2-h intervals for 48 h. Three healthy male volunteers each had their right forearm exposed (in a Plexiglass chamber) for 4 h to DMEA at each of three different levels (250, 500 and 1000 mg/m3 air). Urine was collected up to 24 h after the start of each experiment. DMEA penetrated both guinea-pig and human skin. The median steady-state flux and permeability coefficient (Kp) values, were 0.009 mg/cm2 x h and 0.001 cm/h, respectively, for guinea-pig skin, and 0.017 mg/cm2 x h and 0.003 cm/h, respectively, for human skin. The median uptake in the three volunteers at the different DMEA exposure levels (250, 500 or 1000 mg/m3) was 44, 64 and 88 micrograms, respectively. The median Kp for all experiments was 0.037 cm/h. Uptake of DMEA through the skin is of far less importance than simultaneous uptake via the airways. Thus, the amount of DMEA excreted in urine is a variable of limited use for the purposes of biological monitoring. Although a wide range of Kp values was obtained in the in vitro experiments, both for guinea-pig and human skin, there was no marked difference in median Kp values between the two types of skin. The Kp values were lower than those obtained for human forearm skin in vivo. However, future studies of other tertiary aliphatic amines may show the in vitro method to yield values predictive of those obtained in in vivo studies.

Human mast cell tryptase: a stimulus of microvascular leakage and mast cell activation

We have investigated the potential of tryptase to stimulate an increase in microvascular permeability following injection into the skin of guinea pigs. Tryptase was isolated from high salt extracts of human lung tissue by octyl-agarose and heparin-agarose chromatography. Injection of purified tryptase (2.5 ng–2.5 μg/site) into the skin of guinea pigs which had been injected intravenously with Evans blue dye provoked a dose-dependent increase in microvascular permeability. The skin reactions elicited by tryptase were apparent up to 80 min following injection, while histamine-induced microvascular leakage resolved completely by 40 min. Heat-inactivation of tryptase, or preincubating the proteinase with certain proteinase inhibitors, significantly reduced the extent of microvascular leakage, suggesting dependency on an intact catalytic site. No evidence was found for a synergistic or antagonistic interaction between tryptase (2.5 ng–2.5 μg/site) and histamine (1–10 μg/site) when these mast cell products were injected together. Addition of heparin to tryptase (10:1; w/w) prior to injection was without effect on tryptase-induced microvascular leakage. Pretreatment of guinea pigs with a combination of the histamine H 1 receptor antagonist pyrilamine and the histamine H 2 receptor antagonist cimetidine (both 10 mg/kg), partially abolished tryptase-induced microvascular leakage as well as attenuating the reaction to histamine. Reasoning that the microvascular leakage induced by tryptase is likely to involve the release of histamine, we investigated the ability of tryptase to stimulate histamine release from dispersed guinea-pig skin and lung cells in vitro. Tryptase was found to induce concentration-dependent histamine release from both sources of tissue. Mast cell activation stimulated by tryptase in vitro was inhibited by heat treating the enzyme or by addition of proteinase inhibitors, suggesting a requirement for an intact catalytic site. Histamine release was inhibited also by preincubating cells with the metabolic inhibitors antimycin A and 2-deoxy- d-glucose indicating that the mechanism was energy-requiring and non-cytotoxic. We conclude that human mast cell tryptase may be a potent stimulus of microvascular leakage. The activation of mast cells by this proteinase may represent an amplification process in allergic inflammation.

030 Induction of apoptosis by heat stress in guinea pig skin

030 Induction of apoptosis by heat stress in guinea pig skin

031 The effects of cooling on apoptosis seen in second-degree burned skin of guinea pigs

031 The effects of cooling on apoptosis seen in second-degree burned skin of guinea pigs

Persistence of effects of nitric oxide synthase inhibitors: Comparisons on blood flow and plasma exudation in guinea pig skin

Plasma protein extravasation has been measured in guinea pig skin using 125 I -albumin and blood flow using 133 X enon ( 133 X e) clearance. The nitric oxide (NO) synthase inhibitors N G-nitro- l-arginine methyl ester ( l-NAME), N G-monomethyl- l-arginine (l -NMMA) and N G-nitro- l-arginine ( l-NOArg) and the α-adrenoceptor agonist, phenylephrine, inhibited bradykinin induced plasma protein extravasation when co-injected with the peptide. The inhibitory effects of l-NAME and l-NOArg lasted for up to 8 and 4 h, respectively, whereas phenylephrine and l-NMMA had no persistent inhibitory effects. When co-injected with 133 X e, l-NAME, l-NMMA, l-NOArg and phenylephrine, but not d-NAME, produced significant reductions in skin blood flow. When injected prior to 133 X e, l-NAME and l-NOArg, but not phenylephrine or l-NMMA, significantly reduced flow. The effect of l-NAME on flow was not significant at 8 h. Thus, although the inhibitory effects of the NO synthase inhibitors on mediator induced plasma protein extravasation show correlations with their effects on blood flow, the persistent effect of l-NAME on exudation appears to extend beyond its effect on flow.

In vitro dermal absorption of two commercial formulations of 2,4-dichlorophenoxyacetic acid dimethylamine (2,4-D amine) in rat, guinea pig and human skin

In vitro dermal absorption studies with rat, hairless guinea pig and human skin were conducted employing Bronaugh flow-through cells for two commercial formulations of the herbicide, 2,4-dichlorophenoxyacetic acid dimethyl amine (2,4-D amine) and in vivo studies were conducted with rats. The Clean Crop (CC) and Wilbur-Ellis (WE) 2,4-D amine formulations gave similar absorption values, ranging from 21 to 30% in vitro in all three species, except for absorption from WE in guinea pig skin [16 ± 4.7% (n = 4)], which was significantly less (Student's t-test; P < 0.05) than absorption from WE formulation for human skin [28 ± 2.6% (n = 4)]. A profound ‘washing-in’ effect of the soap wash conducted at 24 hr post-treatment was observed for all three species in vitro, and this effect was much more pronounced than in previous studies with 2,4-D where more dilute topical doses were employed. Dermal absorption of both 2,4-D amine formulations was significantly less for rats tested in vivo (16–17%) than for the skin from the same rats tested in vitro (26–30%). The lower percentage absorption observed in vivo was thought to be due to ‘rub-off’ of the dose application, as 68–78% of the dose was detected in the foam rubber patches used to protect the dose site. The inability to demonstrate greater permeability of animal skin to skin from the one human subject tested, the observation of a soap ‘washing-in’ effect, and the apparent overprediction of field exposure by both the in vivo and in vitro data were all factors considered to have important implications for accurate assessment of occupational exposure to 2,4-D.

Evidence that the eosinophil is a cellular target for the inhibitory action of salmeterol on eosinophil recruitment in vivo

Systemic administration of agents which elevate cyclic AMP (e.g., phosphodiesterase inhibitors, prostanoids, β-adrenoceptor agonists) effectively modulates eosinophil recruitment in vivo. The present study was undertaken to evaluate whether the eosinophil itself is a cellular target for the inhibitory action of these drugs in vivo. We chose to use the long-acting β 2-adrenoceptor agonist salmeterol to test this hypothesis. Eosinophils were pretreated with salmeterol (10 −6 M) before washing and testing in two salmeterol-sensitive systems, namely eosinophil aggregation and 111In-eosinophil accumulation in guinea-pig skin. Pretreatment with salmeterol inhibited by 65% and 43% eosinophil aggregation induced by platelet-activating factor (PAF) and human recombinant C5a, respectively. Similarly, 111In-eosinophil accumulation induced by PAF and zymosan-activated plasma, a source of guinea-pig des-Arg-C5a, was inhibited by 55% and 45%, respectively. In contrast, the level of circulating 111In-eosinophils at 1 h was enhanced by 35% in animals which received salmeterol-pretreated 111In-eosinophils. Our results suggest that the eosinophil itself is one of the cellular targets of the inhibitory action of systemically administered salmeterol on eosinophil recruitment in vivo. © 1997 Elsevier Science B.V. All rights reserved.

An Unexpected Finding in Percutaneous Absorption Observed between Haired and Hairless Guinea Pig Skin

An Unexpected Finding in Percutaneous Absorption Observed between Haired and Hairless Guinea Pig Skin

Effect of phosphatidylglycerol on the in vitro percutaneous drug penetration through the dorsal skin of guinea pigs, and analysis of the molecular mechanism, using (ATR-FTIR) spectroscopy

Standard in vito skin percutaneous penetration methods using excised guinea pig dorsal skin were employed, to characterize the penetration of a water-insoluble drug: tenoxicam (TEX), and a water-soluble drug: diclofenac sodium salt (DFS), enhanced by phosphatidylglycerol (PG); and an attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy was used to analyze the molecular mechanism of the drug penetration route. The C-H bond stretching absorbance frequency shift in the stratum corneum (SC) induced a higher and a broader absorbance, and the shift was dependent on the PG concentrations. The percutaneous penetration of TEX was dependent on the PG concentration (up to 6%). The enhancing mechanism of PG to TEX may not only increase the diffusion coefficient (D) and the partition coefficient (K) in the percutaneous TEX penetration but also increase fluidity of the route (intercellular lipid domain) for TEX, while that of PG to DFS, excepting 1%, PG system, may be increasing the D value in the percutaneous DFS penetration only. The percutaneous penetration of DFS was not dependent on the PG concentrations. Furthermore, the percutaneous penetration of TEX was proportional to the C-H bond stretching absorbance frequency shifts. In contrast, the percutaneous penetration of DFS was not proportional to the C-H bond stretching absorbance frequency shifts. Furthermore, the accumulation of TEX in skin was proportional to the C-H bond stretching absorbance frequency shifts. The striking parallel between the enhancement of the percutaneous penetration of TEX and the measured SC lipid fluidity shifts caused by PG, suggests that the transdermal water-insoluble drug penetration may be ultimately related to the SC lipid structure. Overall, these results suggest that PG mainly affects the intercellular lipid pathway (lipid-rich domains).

Inhibitory effect of acyl-CoA and acyl-carnitine compounds on the ischemia-inducing activity of Bordetella heat-labile toxin in guinea pig skin.

The ability of Bordetella heat-labile toxin (HLT) to induce ischemic lesions after intracutaneous injection to guinea pig skin was lost following incubation at 37 degrees C with long-chain saturated acyl-CoA and acyl-carnitine compounds. Short-chain unsaturated acyl-CoA compounds, however, were less potent in inhibiting the induction of HLT activity. Long-chain saturated acyl-CoA and acyl-carnitine compounds, potently inhibited the induction of this activity. On incubation with HLT at 0 degrees C, a long-chain saturated acyl-CoA compound, palmitoyl-CoA, did not inhibit HLT activity. When first mixed with bovine serum albumin or dimethyl-beta-cyclodextrin, palmitoyl-CoA lost the ability to inhibit HLT activity. Binding of 14C-palmitoyl-CoA to HLT was measured by Scatchard analysis. The Bmax values of HLT (2.75 mol/mol of protein) were higher than that of acyl-CoA-binding protein from bovine liver (0.95 mol/mol of protein). Neither acyl-CoA hydrolase nor acyl-CoA ligase was detected in the HLT preparation. These results suggest that the acyl-CoA and acyl-carnitine compounds bind directly to HLT and produce a critical change in conformation required for HLT activity.

光生物学からみた色素性皮膚病変に対するレーザー療法

Many biomedical applications of lasers have been developed. In many cases, however, selection of a particular laser has been based largely on availability, and treatment protocols have often been developed by an empirical approach. The choice of lasers and exposure parameters must be based on an understanding of the mechanisms of treatment, the optical and thermal properties of the tissue, or rational, theoretical approach to maximize therapeutic benefits and minimize adverse reaction such as scarring. Selective photothermolysis has been proposed as a construct which may be useful in designing laser systems for biomedical applications, especially for the treatment of pigmentary dermatoses. The necessary conditions are (1) tissue structures which preferentially absorb a wavelength of light more than the surrounding tissue,(2) a pulse of light sufficiently short and energetic to produce localized high temperatures in the absorbing structures, and (3) a predominantly thermal mode of initiation of tissue damage. The concept of selective photothermolysis has been confirmed by our gross and ultrastructural observations of albino and black guinea pig skin irradiated with single laser pulses. At present, various kinds of Q-switched lasers, with a pulse of light sufficiently short and energetic enough to produce localized high temperatures in the targets, are used for the treatment of many pigmented skin lesions and demonstrated to be useful for treatment of dermal melanocytosis and black, brown, and blue tattoos which showed no significant response to previous therapies. In the patients with basal pigmentation, however, patients with postinflammatory pigmentation or chloasma show no response, although most patients with solar lentigo and all patients with mucosal pigmentation reveal a good response after only one laser treatment. Therefore, it becomes more important to differentiate several pigmented lesions responsive for laser treatment from the others.

Effect of phosphatidylcholine on the percutaneous penetration of drugs through the dorsal skin of guinea pigs in vitro; and analysis of the molecular mechanism, using attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy

Phospholipids are effective penetration enhancers for the transdermal delivery of certain co-applied drugs. Standard in vitro skin percutaneous penetration methods using excised guinea pig dorsal skin were employed to characterize the comparison with penetration of a water-insoluble drug, prednisolone (PR), and a water-soluble drug, diclofenac sodium salt (DFS) enhanced by phosphatidylcholine (PC) from soybean. An ATR-FTIR spectroscopy was used to analyze the molecular mechanism of enhancement of the drug penetration, and to measure the lipid fluidity in the stratum corneum (SC) of guinea pig skin caused by PC. The C-H bond stretching absorbance frequency shifts in the SC of guinea pigs induced a higher and a broader absorbance shifts, and a shift was dependent on the PC concentrations. In addition, the percutaneous penetration of PR was dependent on the PC concentration (up to 10% concentration). On the other hand, the percutaneous penetration of DFS was not dependent on the PC concentration. Further, the percutaneous penetration of PR was proportional to the C-H bond stretching absorbance frequency shifts. In contrast, the percutaneous penetration of DFS was not proportional to the C-H bond stretching absorbance frequency shifts. Furthermore, the accumulation of PR in skin was inversely proportional to the C-H bond stretching absorbance frequency shifts (without a plot of the control). The accumulation of DFS in skin was inversely proportional to the C-H bond stretching absorbance frequency shifts (without a plot of the control). The striking parallelism between the enhancement of the percutaneous penetration of PR and the measured SC lipid fluidity shifts caused by PC suggests that the transdermal water-insoluble drug penetration may be ultimately related to the SC lipid structure. On the other hand, the non-parallelism between the enhancement of the percutaneous penetration of DFS and the measured SC lipid fluidity shifts measurement caused by PC suggests that the mechanism of the transdermal water-soluble drug penetration may not be intimately related to the SC lipid structure.

Phagocytic and lysosomal activity in Langerhans cells from sensitized guinea pigs

Guinea pig skins were sensitized and challenged with horseradish peroxidase. Langerhans cell granules contained the horseradish peroxidase. The cytoplasmic locations of horseradish peroxidase in Langerhans cells changed with the passage of time: The antigen was found initially in peripheral Langerhans cell granules and subsequently in those located near the nucleus. The number of lysosome-like dense bodies, or multivesicular bodies increased with time. After 24 hr the antigen was absent from the Langerhans cell granules and seen only in lysosome-like dense bodies, or multivesicular bodies. When acid phosphatase activity was examined, the Langerhans cell granules attached to plasma membranes and rodshaped granules were negative. It was positive in lysosome-like dense bodies, multivesicular bodies, and the bulb part of the Langerhans cell granules. A similar sequence of observations was made when guinea pig skins were sensitized and challenged with ferritin and 2,4-dinitro-1-chlorobenzene. It is concluded that Langerhans cell granules can take up antigens and assume an aspect of the lysosome.