The Dermal-epidermal Junction in Psoriasis*

Vol. 53, No. S

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THE DERMAL-EPIDERMAL JUNCTION IN PSORIASIS* ALVIN J. COX, M.D. ABSTRACT

TWO kinds of alteration of the ultrastructure at the dermal-cpidermal junction have been found in lesions of psoriasis. Increase in the amount of basal laminar material, often producing a net-like pattern, has been more prominent in old lesions. Foci of discontinuity in the basal lamina through Which portions of epidermal cytoplasm protrude into the dermis, have been most numerous in active lesions, both recent and old. These relationships suggest that laminar defects precede the proliferation of laminar substance, though the mechanism is not clear. Since similar basal laminar changes have been observed in other cutaneous lesions that exhibit abnormal epidermal growth, it is sugested that basement membrane alterations may be an index of epidermal growth activity, and tbat as such they may be useful in evaluating the activity of psoriatic lesions.

The ultrastructure of the dermal-epidermal Non-neoplastic lesions of the gum have shown junction in psoriatic lesions was examined as comparable change (18), and a similar al-

part of an inquiry on the nature of the pso- teration is pictured in a report on the ultrastructure of halo nevi (20). Whether there was Changes in this region have been described abnormal epidermal growth associated with in psoriasis but reported findings are not con- the latter was not indicated. It appears that sistent. Brody in 1962 called attention to a this type of alteration of the epidermal basal "splitting" of the psoriatic epidermal basal lamina is not specific for any disease, though it lamina as well as to the penetration of small has often been related to abnormal epidermal processes of epidermal cells into the dermis at growth. points of membrane deficiency (1). No parMATERIALS AND METHODS ticular significance was attributed to these observations. Subsequent publications concerned 100 specimens of psoriatic skin used in this with the fine structure of psoriatic lesions study came from 60 patients who were under have not recorded comparable changes (2, 3, 4, prolonged observation in the Stanford University Department of Dermatology. Most had been seen 5,6). repeatedly in the Psoriasis Clinic before biopsy, Focal discontinuity and duplication of the and all were followed subsequently to establish 9pidermal basal lamina like the changes re- the course of the disease after biopsy. Each lesion for biopsy was selected carefully ported by Brody have been described, however, in association with subepidermal bullac after learning from the patient the recent beof his various lesions, particularly the one (7, 8, 9, 10) and in human squamous cell nco- havior selected for ultrastructural study. plasms (11, 12, 13, 14). In several epidermal The specimens fell into four groups. Group I tumors of animals the basal lamina has shown represented 23 lesions less than 1 cm in diameter similar defects (15, 16, 17, 18), and a feature that were explicitly designated by the patients as of the regenerating limb of amphibia is the oc- no more than 3 weeks old. All but 4 of these had been noticed for no more than 2 weeks, and the currence of gaps in the basal lamina which dis- duration of 10 of the lesions was specified as less riatic process.

appear as the regeneration progresses (19). than 1 week. Psoriasis in all of these patients was

clinically active. Group II comprised 18 specimens

Supported by a grant from the John A. Hart- from similar small, apparently recent, lesions that were not specifically dated, but were biopsied Received April 28, 1969; accepted for publica- during periods of clinical activity of the disease. tion July 23, 1969. ford Foundation of New York City.

The technical assistance of Miss Jan Paull was an important contribution to this study.

* From the Department of Dermatology,

Stanford University School of Medicine, Stanford, California, 94305.

17 specimens forming Group III came from larger plaques, present for several months or years, that were sampled during periods of clinical activity as judged by the observed course of the disease over the weeks before and subsequent to biopsy. Group

428

DERMAL-EPIDERMAL JUNCTION IN PSORIASIS

IV contained specimens from lesions, mostly large plaques, that were considered inactive on the basis of sequential clinical observations indicating no extension of lesions or appearance of new lesions immediately before or after the time of biopsy.

429

plasma membrane, replacing the normal thin

lamina (Fig. 1B). The space between the lamina and the plasma membrane of the basal cells was often irregularly increased, reaching a

Most of the patients in the study were not re- width of more than 0.5 micron in places. ceiving vigorous therapy, but no attempt was This appearance of multiple layers of basal made to classify the lesions according to the na- lamina was like that noted by Brody (1) but ture of preceding therapy. Several of the recent lesions had appeared shortly after cessation of was frequently more prominent than that pictured in his illustrations. The deep surface of methotrexate treatment. The specimens were excised with a specially the basal cells was often prominently folded. prepared instrument made from a 15 gauge hypoThe second type of alteration of the epiderdermic needle by cutting off the beveled end and mal basal lamina was often observed without sharpening the remaining circular edge. A single quick twist with moderate pressure against the associated multiplication of layers. Small zones skin surface sufficed to separate a fine core of skin. of discontinuity, or gaps, in the lamina, usually If this remained attached to deep tissue, it was between 0.5 and 5 microns wide, provided separated with fine scissors. Anesthesia was not spaces through which polypoid projections of required since the discomfort of this biopsy procedure was slight, often no more than that of an cytoplasm of basal epiderrnai cells protruded injection of novocaine. The residual puncture into the dermis (Fig. 2). The lamina at the wound healed rapidly, with an almost invisible borders of the gaps often terminated abruptly, scar. sometimes after turning sharply toward the The specimens were fixed 2—3 hours in cold 2% dermis for a short distance. At times there was osmic acid solution in an acetate-veronal buffer

at pH 7.4. After dehydration with increasing con- thinning or irregularity of the lamina at the margin of a gap, and occasionally small defects Vestopal-W. Thin sections, prepared with a Hux- without cell protrusion were present nearby ley ultramicrotome, were surveyed, after staining (Fig. 3A). When basal cell cytoplasm prowith uranyl acetate and lead citrate, in a Phillips truded through laminar gaps, it assumed a EM 75 or an RCA EMU-3 electron microscope. The dermal epidermal junction was examined care- variety of shapes, including slender, finger-like

centrations of acetone they were embedded in

Iully over the width of each specimen. RESULTS

In most respects the changes at the dermalepidermal junction in psoriatic lesions were not distinctive, as has been pointed out by others. There were alterations relating to the

processes, broad-based shallow protrusions, and complex bulbous projections, some with multiple secondary extensions from the sur-

face. Not infrequently more than one cell process passed through the same basal laminar defect; these protrusions sometimes resembled swollen microvilli. Some of the epidermal proc-

basal lamina, however, which were sufficiently esses were broader on the dermal side of the prominent to warrant analysis. These changes basal lamina t.han the width of the defect have been considered in two categories: (1) through which they protruded (Fig. 2B). This modification of the lamina to form multiple resulted in their presence in sections that did layers, and (2) focal deficiency of the lamina. not include a laminar defect. Though clearly

When the former abnormality was mild, it continuous with the cytoplasm of epidermal was often characterized by intradermal pro- basal cells, the protruded cell processes usually jections of homogeneous lamellar material from did not possess the larger cytoplasmic orpoints of contact with normally situated por- ganelles that were present elsewhere in the cell tions of the basal lamina (Fig. lA), and such body. Mitochondria and tonofibrils were absent projections sometimes formed bridges attached in the protruded cytoplasm, as if they had at their margins to a layer occupying a normal been specifically withheld from the protruding position (Fig. 1B). When the change was more processes. These epidermal cell protrusions were situpronounced multiple layers of membrane-like material formed a meshwork that incorporated ated at different relative positions along the basal cell border. Frequently they were near elements of the superficial dermis (Fig. 1C). These abnormal layers of lamellar structure the lateral margins of the cells, and at times were usually thicker than the normal lamina; portions of two adjacent basal cells protruded

they sometimes lay close to the basal cell through the same basal laminar defect (Fig.

430

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FIG. 1. Duplicated epidermal basal lamina in psoriatic plaques. Thin arrows indicate

normal-appearing lamina; thick arrows designate abnormal laminar material. A. 0< 17,000) Thick arrows point to curved projections from the normal layer. B. 0< 24,000) Thick arrows

identify bridges of added laminar material, some of which appears to have replaced the normal layer. In 0. (X 29,500) a net-like pattern has been formed by abnormal bcsal lamjna. D, dermis. 0, cytoplasm of basal cell containing tonofibrils; S, wide intercellular space.

3B). Occasionally an epidermal cell process was unassociatcd with any protrusion of the and a pseudopod of a wandering cell pro- adjacent cell membrane. Whether these gaps truded tbrougb the same laminar defect. Here represented the same kind of defect as those and there a small zone of laminar discontinuity harboring cell protrusions has not been de-

DERMAL-EPIDERMAL JUNCTION IN PSORIASIS

FIG.

431

2. Basal laminar defects in recent psoriatic lesions (X 24,000). Arrows indicate

borders of openings through which epidermal cells protrude. A. (X 17,000) is from a 2 week old lesion. B. (X 24,000) is from a 3 day old lesion. C. (X 24,000) shows a defect opposite a cell junction. The protruding cytoplasmic process is long and thin. D, dermis; C, cytoplasm of epidermal basal cell; N, nucleus.

termined. When there were multiple layers of basal lamina, epidermal cell protrusions sometimes extended through gaps in the ad-epider-

mal portion but were partly or completely

covered by deeper layers of laminar material (Fig. 3C).

A difference in the frequency of basal laininar changes was observed in different types of

432

THE JOURNAL OF INVESTIGATIVE DERMATOLOGY

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Fm. 3. Basal laminar defects in active psoriatic lesions. Thick errows indicate openings that border epidermal cell protrusions. A. (X 21,000) shows irregularities of the lamina near the opening (thin arrows). B. (X 23,000) shows processes of two basal cells protruding through the same opening. C. (x 24,000) shows laminar duplication partly surrounding a protruding basal cell process. ID, dermis; C, cytoplasm of epidermal basal cell.

psoriatic lesions. To obtain an estimate of the number of laminar gaps in each specimen, the defects were counted and were recorded for each specimen as the number per millimeter of

dermal-epidernial border. For practical rea-

sons this measurement did not follow the finest undulations of the border, so the recorded frequency is only an approximation.

433

DERMAL-EPIDERMAL JUNCTION IN PSORIASIS

TABLE I In order to avoid including artifactual defects in the basal lamina or defects induced by Comparison of epidermal basal laminar gaps* f different lesions from the same patient infiltrating wandering cells, no gap was counted unless it contained a projection from an adjaShortest time cent basal cell, identified either by cytoplasmic Patient Inactive lesion Active lesion between biopsies (months) continuity or by the characteristic clear con-

tent, without major cell organelles, and the Absence of any nearby wandering cell that could have contributed such a process.

The frequency of gaps in the basal lamina in the four groups of psoriatic specimens de.scribed in the section on material and methods

is illustrated in Figure 4. The first three of these groups, which represented presumably

A

1

15

B

0

C D

4

141 28

1

E F

9 3

9t

3/4

2

G H

1

9

6

11

J

4* 3

3 3 3 4 5 6

0

9

6

7

20 22

active lesions, presented a similar incidence of

I

basal laminar defects. All but 3 of these 58 lesions had more than 2 gaps per mm of der-

K

20t 6 12

mal-epidermal border, and in only 1 was it imExpressed as number per millimeter of dermalpossible to find any laminar discontinuity. Of epidermal border. the 42 lesions classed as inactive, however, 11 f Average of two or more lesions. exhibited no laminar gaps, and 12 more presented only 1 or 2 per mm. There was no clear The less active lesion was biopsied first in 6 of difference between chronic lesions thought to the patients; in the others the sequence was be stationary and those regarded as involut- reversed. Patient A was observed in an acute ing. guttate flare at the onset of his disease, when There were differences in the number of there were numerous gaps in the basal lamina. basal laminar gaps in different lesions from the Topical application of fluocinolone acetonide same patient at different times. Eleven groups (Synalar) was followed by a striking involution of sequential observations are listed in Table I. of the process; after one week only one basal laminar defect could be identified in a second EPIDERMAL BASAL LAMINAR DEFECTS biopsy specimen. In neither lesion could pro0-2 PER MM. OF CELL BORDER

3-8 I4

nounced laminar duplication be observed.

30

The frequency and prominence of multiple layers of basal laminar material did not relate closely to the amount of laminar deficiency. Laminar duplication was more pronounced in old than in recent plaques, and was of about the same degree whether or not chronic lesions were active. The amount of multiplication of laminar structures could not be subjected to exact quantitation, as it was frequently different from place to place, but the estimated de-

I-. 20

gree of this change was recorded for each speci-

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men. Marked alteration of this type occurred more than twice as frequently in the chronic lesions as in the recent plaques, and more than LARGE INACTIVE SMALL % of the instances of marked laminar duplicaRECENT ACTIVE ACTIVE tion represented chronic lesions, without any (42) (17) (18) (23) differences related to estimated activity of the CHARACTER OF PSORIATIC LESIONS Fic. 4. Incidence of epidermal basal laminar disease. A more detailed analysis of these very defects in psoriastic lesions of different types. rough quantitative estimates does not appear Figures in parentheses indicate numbers of lesions 10

i11i iLL

in the respective groups.

justified.

434

THE JOURNAL OF INVESTIGATIVE DERMATOLOGY DISCUSSION

enhancing basal cell nutrition through increas-

ing the surface area of the basal cells or by

Reference to the published reports quoted closer approximation of the basal cell surface above leaves little doubt that the changes in to the source of nutritive supply. the epidermal basal lamina in psoriasis arc Whether the basal laminar changes in subcomparable to those observed in other condi- epidermal bullous lesions represent the same

tions, including squamous cell neoplasms. We mechanism is unknown, though the possibility

have encountered similar, though less pro-

nounced, changes beneath acanthotic epidermis

exists that they are related to epidermal re-

generation subsequent to the cutaneous injury in a variety of diseases; even in apparently in these diseases. The interpretation of the re-

normal skin we have observed patches of mild laminar multiplication and rarely a small focus of discontinuity (21). The lack of specificity of these changes is not surprising since the epidermal growth in psoriasis resembles that of other types of epidermal hyperplasia in many ways. These observations demonstrate that no malignant potentiality is implied by basement membrane changes of the kinds described here. The ultrastructural appearance has provided

ported similar basal laminar changes after experimental dermal injection of clostridial col— lagenase (23) and after surface application of a cream containing hydroxyanisole (24) is also

uncertain. It is not clear from the reports of these observations whether any epidermal growth stimulation had been induced, but this

may have occurred, since epidermal growth may be readily increased by various agents.

quantity of basal lamina missing from little to indicate the mechanism of the basal theThe sites of observed discontinuity in psoriatic laminar discontinuity in active psoriasis. The lesions is small. This may mean that the loss adjacent dermis was not consistently different from that of the superficial dermis elsewhere. is insignificant, though this need not be so if Mitosis was not observed in epidermal cells the formation and repair of these defects is rapid. Kahl and Pearson observed that the adjacent to the laminar gaps. The similarity of basal lamina sometimes disappeared within one those at sites of penetration by wandering minute of the injection of collagenase (23). It cells suggests the possibility that in both in- is possible that focal laminar destruction may stances defects may have been induced by the be repeated many times during the formation of multiple layers of laminar material. penetrating cells, perhaps through the action of The basal laminar gaps of recent psoriatic

the gaps that contained basal cell processes to

a lytic enzyme. Whatever the significance of the laminar discontinuity, such a distinctive change may be presumed to reflect some functional alteration at the dermal-epidermal junction. The regular occurrence of basal cell protrusion at the sites of laminar gaps, and the

plaques, often unassociated with laminar duplication, apparently preceded the development of the latter, which was most prominent in old

lesions. It is logical to suspect that the gaps constituted a precursor of the duplication, as has been suggested also by the sequential observations of Woods and Smith in experimen-

different incidence of defects in different types of psoriatic lesions, provide evidence that these tally induced tumors of the hamster cheek changes are not artifacts. The prominent basal laminar changes in some pouch (18). The abundance of the basal laminar material cases of psoriasis, a disease characterized by

very rapid cpidermal growth (22), and par- when there were multiple layers requires the ticularly the relationships that have been identified between the changes at the dermal-epi-

assumption that there was elaboration of new

disease, are consistent with the hypothesis that the basal laminar defects in some way represent epidermal growth activity. The similar changes in other epidermal proliferative processes probably have the same significance. It is possible

the source of the basal lamina. The possibility has been considered that the disturbance of the

laminar substance. Current opinion (25, 26, 27)

dermal junction and clinical activity of the supports the concept that epidermal cells are

basal lamina, prominent in early psoriatie lesions, leads to downward displacement of

segments of old lamina and that these are rethat the epidermal cytoplasmic protrusions placed rapidly by new lamina in the normal into the dermis may aid the rapid growth by position. In view of the fact that dermal col—

DERMAL-EPIDERMAL JUNCTION IN PSORIASIS

lagen fibers surround the abnormal laminae, without exhibiting any indication that they

435

An electron microscopic study of cancer in

situ and invasive carcinoma of the cervix uteri. Cancer Res., 20: 357, 1960.

have been correspondingly displaced, the find- 12. Ashworth, C. T., Stembridge, V. A. and Luibel, F. J.: A study of basement membranes of ings are more readily explained by the view

that new laminar material is precipitated within the superficial dermis deep to the normal position.

The activity of psoriasis cannot be identified precisely on the basis of clinical observation, which provides only impressions and does not

normal epithelium, carcinoma in situ and invasive carcinoma of uterine cervix utilizing electron microscopy and histochemical methods. Acta Cytologica, 5: 369, 1961.

13. Hinglais-Guillaud, N., Moricard, R. and Bern-

hard, W.: Ultrastructure des cancers pavi-

menteux invasifs due col uterin chez la

femme. Asso. Franc, pour l'étude du cancer, 48: 283, 1961,

identify any fluctuations of growth activity 14. Sugar, J.: An electron microscopic study of early invasive growth in human skin tumours over short periods, such as have been postu-

and laryngeal carcinoma. Europ. J. Cancer,

lated in this disease (28, 29). Although much 4: 33, 1968. care was taken in classifying the lesions of this 15. Frei, J. V.: The fine structure of the basement membrane in epidermal tumors. J. Cell. Biol., study with respect to their apparent activity, 15: 335, 1962. the result is not free from uncertainty. It seems 16. Fasake, E. and Morgenroth, K.: Electron mi-

likely that the ultrastructure of the dermalepidernial junction may provide a better index of activity of the psoriatic process than can be derived from clinical estimates.

REFERENCES 1. Brody, I.: The ultrastructure of the epidermis in psoriasis vulgaris as revealed by electron microscopy. 1. The dermoepidermal junction and the stratum basale in parakeratosis

without keratohyalin. J. Ultrastr. Res., 6: 304, 1962.

2. von Wettatein, D., Lagerhoim, B. and Zech, H.: Cellular changes in the psoriatic epidermis. Acts Dermatovener., 41: 115, 1961. 3. Meirelles Pinto, M. I., Falcao, L., Cruz-Sobral,

croscopic studies on the relation of the base-

ment membrane to the squamous cell carcinomas in animals. Oncologial, 20: 113, 1966.

17. Tarin, D.: Sequential electron microscopical study of experimental mouse skin carcinogenesis. mt. J. Cancer, 2: 195, 1967.

18. Woods, D. A. and Smith, C. J.: Ijltrastructure of the dermal-epidermal junction in experi-

mentally induced tumors and human oral

lesions. J. Invest. Derm., 52: 259, 1969.

19. Salpeter, M. M. and Singer, M. Differentiation

of the submicroscopic adepidermal mem-

brane during limb regeneration in adult

Triturus, including a note on the use of the term basement membrane. Anat. Rec., 136: 27, 1960.

20. Swanson, J. L., Wayte, D. M. and Helwig, E. B.: Ultrastructure of halo nevi. J. In-

F. and Morato, M. J. X.: Etude sur le

vest. Derm., 50: 434, 1968. 21. Cox, A. J. Unpublished observation.

kopische Befunde bei Psoriasis vulganis unter Fluocinolon-acetonid. Hautarzt, 16: 483,

23. Kahl, F. R. and Pearson, R. W.: iJltrastruetural studies of experimental vesiculation. II Col-

5. Lagerholm, B.: Cellular changes in the psoni-

24. Seal, P., Riley, P. A. and Inman, D. R.: Basal

glycogène de l'epiderme normal et psori- 22. Weinstein, G. D. and Van Scott, E. J. Autoradiographic analysis of turnover times of atique. Ann. Den. Syph. (Paris), 90: 497, 1963. normal and psoriatic epidermis. J. Invest. 4. Kalfoff, K. W. and Berger, H.: SubmikrosDerm., 45: 257, 1965. 1965.

atic epidermis. Acta Denmatovener., 45: 99, 1965.

lagenase. J. Invest. Derm., 49: 616, 1967.

cell encroachment into the dermis caused

by applications of hydroxyanisole. J. Invest.

6. Hashimoto, K. and Lever, W. F.: ElektronenDerm., 52: 264. 1969. mikroskopische Untersuchungen der Haut- 25. Hay, E. D. and Revel, J. P.: Autoradiographic Psoriasis. studies of the origin of the basement memDen. veränderungen bei Wchnschr., 152: 713, 1966. brane in Ambystoma. Develop. Biol., 7: 152, 1963. 7. Caufield, J. B. and Wilgram, G. F.: An elec26. Kurtz, S. M. and Feldman, J. D.: Experimental tron microscopic study of blister formation studies on the formation of the glomerular in erythema multiforme. J. Invest. Derm., basement membrane. J. Ultrastruct. Res., 6: 39: 307, 1962. 8. Pearson, R. W.: Studies on the pathogenesis 19, 1962. of epidermolysis bullosa. J. Invest. Derm., 27. Pierce, G. B., Jr., Beals, T. F., Sri Ram, J. and 39: 551, 1962. Midgley, A. R., Jr.: Basement membranes, 9. Wilgram, G. F.: Pemphigus and bullous IV Epithelial origin and immunologic cross pemphigoid. Ultrastructure of Normal and reactions. Amer. J. Path,, 45: 929, 1964. Abnormal Epidermi.s. Ed., Zelickson, A. S., 28. Hell, E. and Hodgson, C.: The uptake of Lea & Febiger, Philadelphia, 1967. 3H-thymidine by epidermal cells in normal

10. Fry, L. and Johnson, F. R.: Electron mi-

croscopic study of dermatitis herpetiformis. Brit.J. Derm., 81: 44, 1969.

11. Luibel, F. J., Sanders, E. and Ashworth, C. T.:

and psoriatic subjects. DNA synthesis in psoriasis. Brit. J. Derm., 78: 262, 1966. 29. Farber, E. M. and Cox, A. J.: The biology of psoriasis. J. Invest. Derm., 49: 348, 1967.

THE JOURNAL OF INVESTIGATIVE DERMATOLOGY

94

linolenic acid extract. Arch. This pdf is a scanned copy UV of irradiated a printed document.

24. Wynn, C. H. and Iqbal, M.: Isolation of rat

skin lysosomes and a comparison with liver Path., 80: 91, 1965. and spleen lysosomes. Biochem. J., 98: lOP, 37. Nicolaides, N.: Lipids, membranes, and the 1966.

human epidermis, p. 511, The Epidermis

Eds., Montagna, W. and Lobitz, W. C. Acascopic localization of acid phosphatase in demic Press, New York. human epidermis. J. Invest. Derm., 46: 431, 38. Wills, E. D. and Wilkinson, A. E.: Release of 1966. enzymes from lysosomes by irradiation and 26. Rowden, C.: Ultrastructural studies of kerathe relation of lipid peroxide formation to tinized epithelia of the mouse. I. Combined enzyme release. Biochem. J., 99: 657, 1966. electron microscope and cytochemical study 39. Lane, N. I. and Novikoff, A. B.: Effects of of lysosomes in mouse epidermis and esoarginine deprivation, ultraviolet radiation and X-radiation on cultured KB cells. J. phageal epithelium. J. Invest. Derm., 49: 181, 25. Olson, R. L. and Nordquist, R. E.: Ultramicro-

No warranty is given about the accuracy of the copy.

Users should refer to the original published dermal cells. Nature, 216: 1031, 1967. version of1965. the material. vest. Derm., 45: 448, 28. Hall, J. H., Smith, J. G., Jr. and Burnett, S. 41. Daniels, F., Jr. and Johnson, B. E.: In prepa1967.

Cell Biol., 27: 603, 1965.

27. Prose, P. H., Sedlis, E. and Bigelow, M.: The 40. Fukuyama, K., Epstein, W. L. and Epstein, demonstration of lysosomes in the diseased J. H.: Effect of ultraviolet light on RNA skin of infants with infantile eczema. J. Inand protein synthesis in differentiated epi-

C.: The lysosome in contact dermatitis: A ration. histochemical study. J. Invest. Derm., 49: 42. Ito, M.: Histochemical investigations of Unna's oxygen and reduction areas by means of 590, 1967. 29. Pearse, A. C. E.: p. 882, Histochemistry Theoultraviolet irradiation, Studies on Melanin, retical and Applied, 2nd ed., Churchill, London, 1960.

30. Pearse, A. C. E.: p. 910, Histacheini.stry Thearetscal and Applied, 2nd ed., Churchill, London, 1960.

31. Daniels, F., Jr., Brophy, D. and Lobitz, W. C.: Histochemical responses of human skin fol-

lowing ultraviolet irradiation. J. Invest. Derm.,37: 351, 1961.

32. Bitensky, L.: The demonstration of lysosomes by the controlled temperature freezing section method. Quart. J. Micr. Sci., 103: 205, 1952.

33. Diengdoh, J. V.: The demonstration of lysosomes in mouse skin. Quart. J. Micr. Sci., 105: 73, 1964.

34. Jarret, A., Spearman, R. I. C. and Hardy, J. A.:

Tohoku, J. Exp. Med., 65: Supplement V, 10, 1957.

43. Bitcnsky, L.: Lysosomes in normal and pathological cells, pp. 362—375, Lysasames Eds., de Reuck, A. V. S. and Cameron, M. Churchill, London, 1953.

44. Janoff, A. and Zweifach, B. W.: Production of inflammatory changes in the microcirculation by cationic proteins extracted from lysosomes. J. Exp. Med., 120: 747, 1964.

45. Herion, J. C., Spitznagel, J. K., Walker, R. I. and Zeya, H. I.: Pyrogenicity of granulocyte lysosomes. Amer. J. Physiol., 211: 693, 1966.

46. Baden, H. P. and Pearlman, C.: The effect of ultraviolet light on protein and nucleic acid synthesis in the epidermis. J. Invest. Derm.,

Histochemistry of keratinization. Brit. J. 43: 71, 1964. Derm., 71: 277, 1959. 35. De Duve, C. and Wattiaux, R.: Functions of 47. Bullough, W. S. and Laurence, E. B.: Mitotic control by internal secretion: the role of lysosomes. Ann. Rev. Physiol., 28: 435, 1966. the chalone-adrenalin complex. Exp. Cell. 36. Waravdekar, V. S., Saclaw, L. D., Jones, W. A. and Kuhns, J. C.: Skin changes induced by

Res., 33: 176, 1964.