Experimental dermatophytosis in mice: correlation between light and electron microscopic changes in primary,secondary and chronic infections.

The histopathological and electron microscopic features of experimental dermatophytosis due to Trichophyton quinckeanum in Balb/c mice have been studied in animals with primary, secondary and chronic infections. Infected animals all showed pathological changes with adherence of microconidia to keratinocytes within 4 h of infection. Other features were the early infiltration of neutrophils, the formation of a mycelial mass (scutulum) in the epidermis, and epidermal oedema. Increased thickness of the epidermis was measured within 3 days of infection, although this was mainly due to oedema. The main differences seen in secondary infections were the paucity of fungal elements, even after 24 h, a sustained increase in epidermal thickness, and the dense dermal infiltrate of mononuclear cells. Chronically infected animals showed similar changes to those at the peak of a primary infection, but in addition there were large numbers of mast cells in the dermis. Cells carrying Ia markers were identified in the epidermis (Langerhans cells) and the dermis (macrophages) in all infections and their distribution did not appear to change. Although recovery from infection has been correlated previously with T lymphocyte mediated responses an increase in the number of cell layers of the epidermis and a dense infiltrate of neutrophils at the zone of infection were both seen within 2 days of infection. It is suggested that neutrophil killing of fungi and increased epidermal proliferation, not dependent on T cell activation, may also be implicated in host defence against dermatophytes.     

Pustular drug eruptions: a histopathological spectrum

We have reviewed the histopathological features of 11 patients with pustular drug eruptions. Two main histological patterns were seen. Eight cases revealed features of toxic pustuloderma with the presence of spongiform intra-epidermal pustules in association with papillary oedema and a mixed inflammatory cell infiltrate around upper dermal blood vessels. Pustules were present at different levels within the epidermis. The other three cases exhibited leucocytoclastic vasculitis with neutrophil collections both below and within the epidermis. One case showed continuity between the subepidermal and intra-epidermal pustules. These findings suggest a dynamic process in which neutrophils collect around upper dermal blood vessels and are then eliminated via the overyling epidermis. The presence of extravasated red blood cells within the intra-epidermal pustules indicates that this process is passive rather than the result of specific chemotaxis or cell migration.     

Participation of neutrophils and delayed hypersensitivity in the clearance of experimental cutaneous candidiasis in mice.

Involvement of neutrophils and delayed hypersensitivity in the clearance of Candida albicans infections was investigated with the use of a model of the disease in inbred mice. Experimental infections were produced by rubbing C albicans onto the shaved skin of the flank without the use of occlusive dressings. After a single infection, delayed hypersensitivity to Candida developed in C57BL/6 mice, and the infection cleared more rapidly than in C3H/He mice, in which delayed hypersensitivity did not develop. In both strains, the organisms were associated with neutrophilic microabscesses in the upper epidermis within 1 day of inoculation; by 3 days, the organisms and microabscesses had become relocated to a site just above the skin surface. At this time, the epidermis was intact under the microabscesses and significantly thickened, which indicated that epidermal proliferation had occurred. Delayed hypersensitivity reactions accelerated clearance of the infection, apparently by increasing the rate of removal of the microabscesses and associated organisms from the skin surface. However, delayed hypersensitivity was not an absolute requirement for clearance, because in animals of the C3H/He strain, in which delayed hypersensitivity did not develop during the first infection, the infection was eventually cleared. It is postulated that in these infections an important defense mechanism may be the enhancement, perhaps by the neutrophilic infiltrate, of epidermal proliferation early in the infection such that the infecting organisms are moved to a location above the skin surface from which they can be more easily removed by other processes, including delayed hypersensitivity reactions.     

Regression beim Melanom

Malignant melanoma is a neoplasm that more often tends to undergo regression. Clinically, variation in color is perhaps the most important hallmark of primary cutaneous melanoma. The change in color to white, off-white, blue-white and gray-white is a sign of (spontaneous) regression in malignant melanoma. Histopathologically the process starts with a dense lichenoid infiltrate of lymphocytes, and ends with fibrosis and/or melanosis within a thickened papillary dermis. The dense infiltrate of lymphocytes permeates the thin melanoma and destroys the atypical melanocytes in the epidermis and the papillary dermis. A key concern is how to define regression in a reproducible way. Using the following definition, a statistically significant risk of metastases can be demonstrated in thin melanomas (<1.0 mm) with extensive regression (>50%): "fibroplasia with an absence of epidermal and dermal involvement by melanoma cells, but allowing for (lentiginous) single-cell proliferation of atypical melanocytes along the dermo-epidermal junction".     

Melanocyte Changes in Epidermal Hyperplasia—An Experimental Study

Subepidermal injection of suspensions of silica in guinea-pigs produces granulomatous inflammation in the dermis and hyperplasia of the overlying epidermis. In the experiments described here this procedure was adopted in 16 animals in order to investigate the behaviour of the melanocytes in the hyperplastic epidermis. The DOPA reaction was used to identify melanocytes and the number of DOPA positive cells per 100 basal epidermal cells (DOPA index) was correlated with the degree of epidermal hyperplasia. The epidermal reaction was charted by estimating the autoradiographic labelling index after injection of tritiated thymidine and measuring the epidermal thickness. The DOPA index fell in the hyperplastic epidermis and had not returned to control levels by three weeks. However, there were foci within the epidermis where the number of melanocytes and their reactivity appeared to be increased. The number of “clear cells” in the basal epidermis was also estimated and the numbers of these cells approximately paralleled the changes in the DOPA positive cells. Silver staining for melanin did not demonstrate pigmentary incontinence.     

Histopathology of endocervical infection caused by Chlamydia trachomatis, herpes simplex virus, Trichomonas vaginalis, and Neisseria gonorrhoeae

We determined the histologic correlates of clinically identified mucopurulent cervicitis, culture-proven cervical infection with Chlamydia trachomatis, Neisseria gonorrhoeae, herpes simplex virus (HSV), and vaginal infection with Trichomonas vaginalis by examining cervical biopsies from 83 women. Clinical mucopurulent cervicitis and culture-documented infection with one or more of these pathogens correlated histologically with intraepithelial neutrophils, reactive endocervical cells, edema, luminal neutrophils, and with several deeper tissue changes such as extensive and dense subepithelial inflammation, granulation tissue, and necrotic ulceration. Focal loss of surface columnar cells and spongiosis were also correlated with culture-confirmed infection. Well-formed germinal centers were seen in biopsies from 14 of 21 patients (67%) with C trachomatis infection alone, but in none of 17 patients with infections other than C trachomatis (P less than 0.001). A predominantly plasmacytic infiltrate was also significantly associated with chlamydial infection. Necrotic ulcers overlying a predominantly lymphocytic infiltrate were seen in six of nine patients (67%) with HSV infection alone but in only two of 40 patients (5%) with other infections (P less than 0.001). Marked inflammatory changes were not seen in the patients infected with N gonorrhoeae. The organism T vaginalis was not associated with any endocervical pathology. If these results are confirmed by prospective studies, they suggest that pathologists should alert clinicians to the possibility of recent or current infection with C trachomatis or HSV when cervical biopsies show the above changes. The loss of surface columnar epithelium with HSV, chlamydial, and gonococcal infection offers a possible explanation for the reported association of these infections with increased risk of acquiring human immunodeficiency virus infection.     

The exanthem of Ross River virus infection: histology, location of virus antigen and nature of inflammatory infiltrate

The exanthem of epidemic polyarthritis, a disease caused by Ross River (RR) virus, was examined three days after onset of the common erythematous and the rare purpuric forms of the eruption. The dermis showed a light perivascular infiltrate of mononuclear cells in both, with extravasation of erythrocytes in the latter. No immunoglobulins (IgM, IgG, IgA) or complement components (Clq, C3) were detected. Most of the infiltrating cells were T lymphocytes of the T suppressor-cytotoxic class. Their perivascular location, the scarcity of other lymphocytes or phagocytes, and rapid resolution of the rash indicated that the T lymphocytes were responsible for cytotoxic destruction of virus-infected cells. A few monocyte-macrophage cells were identified in the perivascular infiltrate. RR virus antigen was found in the basal epidermal and eccrine duct epithelial cells of both types of lesion and in the perivascular zone of the erythematous lesion, but appeared to have been eliminated from this region in the purpuric lesion. It is suggested that secondary effects of the T-cytotoxic reaction on nearby capillaries are responsible for erythema, oedema and purpura in the exanthem.     

Neutrophil accumulation and cutaneous responses in experimental cutaneous candidiasis of genetically complement-deficient mice

Mice deficient in the fifth component of complement were studied for their ability to respond to and clear experimental cutaneous Candida albicans infections. The complement-deficient animals took longer to clear the infections and developed a significantly greater delayed hypersensitivity response to Candida than did normal animals. However, although the serum of the complement-deficient animals was incapable of generating in vitro chemotactic activity for neutrophils after appropriate stimulation, the epidermal neutrophilic infiltrate in the Candida-infected skin of these animals was equivalent to that in the normal animals. The progression of the infection, including the early relocation of the invading Candida pseudohyphae to a more superficial site in the stratum corneum and the thickening of the epidermis itself, was also similar in the complement-deficient and normal animals. Therefore, although mice lacking the fifth complement component cannot generate complement-derived serum chemotactic factors and are somewhat less efficient in clearing experimental cutaneous candidiasis, the accumulation of neutrophils in the Candida-infected skin of these animals and their initial cutaneous responses to the infections are normal.     

Neural modulation of cutaneous differentiation: epidermal hyperplasia and precocious hair development following partial neuralectomy in opossum pups

The original intent of the present study was to evaluate the compensatory response of the nervous system to areas of denervation. A portion of the spinal cord in the lumbosacral region of one-day opossum pups (Monodelphis domesticus) was removed by cauterization. This partial neuralectomy produced an expected compensatory response of neurons in the dorsal root ganglia, but in addition produced unexpected abnormalities of cutaneous differentiation. At 4-6 days following surgery, an increase in the thickness of the epidermis resembling glabrous palmar or plantar skin was seen. This hyperplastic epidermis appeared to be associated with an abnormally dense innervation of the dermis and epidermis. Eight days following partial neuralectomy most animals showed areas of precocious hair development. Nerve fibers were always seen in the dermis associated with these precocious hairs and were seen to penetrate the basal lamina in the region of the epidermal-hair shaft boundary. These results imply a critical role for afferent nerves in the normal development of the skin and its appendages.     

CCR7 governs skin dendritic cell migration under inflammatory and steady-state conditions

The CC chemokine receptor CCR7 has been identified as a key regulator of homeostatic B and T cell trafficking to secondary lymphoid organs. Data presented here demonstrate that CCR7 is also an essential mediator for entry of both dermal and epidermal dendritic cells (DC) into the lymphatic vessels within the dermis while this receptor is dispensable for the mobilization of Langerhans cells from the epidermis to the dermis. Moreover, a distinct population of CD11c(+)MHCII(high) DC showing low expression of the costimulatory molecules CD40, CD80, and CD86 in wild-type animals was virtually absent in skin-draining lymph nodes of CCR7-deficient mice under steady-state conditions. We provide evidence that these cells represent a semimature population of DC that is capable of initiating T cell proliferation under conditions known to induce tolerance. Thus, our data identify CCR7 as a key regulator that governs trafficking of skin DC under both inflammatory and steady-state conditions.     

Morphology of atopic eczema

The routine examination of skin biopsy specimens embedded in paraffin and strained with hematoxylin-eosin has failed to allow differentiation of atopic eczema from other types of eczematous dermatitis. The use of 1-μm plastic-embedded sections permits the recognition of in filtrating cell types and blood vessel alterations, thus allowing a refined method to examine cutaneous lesions and permit better definition of cutaneous structures than can be achieved in routinely-processed specimens.
Acute vesicular lesions exhibited marked epidermal intercellular edema (spongiosis) and a dermal inflammatory infiltrate of lymphocytes, and activated lymphocytes with normal numbers of mast cells that exhibited various degrees of hypogranulation. Only rare eosinophils, neutrophils, and basophils were noted. Venular alterations included endothelial cell hypertrophy without necrosis. In lichenified plaques there was epidermal hyperplasia with a dermal inflammatory infiltrate that included increased numbers of fully granulated mast cells and increased numbers of lymphocytes and monocyte-macrophages. Alterations of venules included marked endothelial cell hypertrophy and basement membrane thickening. Cutaneous nerves exhibited demyelination and fibrosis.
Also, increased numbers of Langerhans' cells have been noted in the epidermis of chronic lesions. Despite the absence of eosinophils, major basic protein has been demonstrated in the dermis by direct immunofluorescence techniques. Studies of lymphocyte subsets have shown increased numbers of CD4 + T lymphocytes.     

Histopathological and ultrastructural studies on human cutaneous leishmaniasis

Leishmania, a genus of intracellular protozoan parasites of macrophages, is the etiologic agent of cutaneous and visceral disease in man. In our study, localized cutaneous infections with leishmania were studied by light and transmission electron microscopy in 16 patients at phases ranging from onset to a progressive disease. In early infections, epidermal changes could be detected as deep hemorrhagic ulcer characterized by focal massive necrosis of the epidermal layers. Spongiotic vesicles in the epidermis were prominent containing the amastigotes. The dermal changes appeared in the form of diffuse inflammatory infiltrate predominantly composed of macrophages, epithelioid cells, lymphocytes, mast cells, and few plasma cells and eosinophils. Macrophages laden with the parasites were seen dissociating the striated muscle and the collagen bundles which showed degenerative and necrotic changes. In late stages of the disease, multiple granulomas formed predominantly of macrophages containing promastigotes and amastigotes, giant cells, epithelioid cells, and some mast cells were seen in the dermis. Some macrophages appeared vacuolated and loaded with the parasite. The dermal vasculature showed congestion, swelling of the endothelial cells, and fibrinoid necrosis of the wall. Some congested blood vessels demonstrated margination and diapedesis of inflammatory cells. By transmission electron microscopy, intact and degenerated amastigotes were seen phagocytosed inside the macrophagal parasitophorus vacuoles. Erythrophagocytosis and the reaction of other inflammatory cellular components were also described. These results clarified the lesions of leishmania invasion into the skin of the affected patients and its defensive mechanism. Moreover, the host macrophagal–parasite relationship was shown on ultrastructural level.     

Tetranectin expression in human colonic neoplasia

Pigmented lesions of palmar and plantar skin may cause diagnostic problems, partly because they are infrequently excised and also because some features of benign lesions in these sites may raise the suspicion of melanoma if considered alone. We have examined a series of benign melanocytic lesions and compared them with melanomas from these sites. The presence of severe melanocytic atypia was the most valuable feature in distinguishing between naevi and melanomas. Pagetoid infiltration of the epidermis by single atypical cells, or small groups of cells with abundant pale cytoplasm was seen only in melanomas, while transepidermal elimination of well-circumscribed nests was present only in benign lesions. A lymphocytic infiltrate was present in the dermis in 13 of 14 malignant lesions, but only two of the 26 naevi showed a sparse infiltrate: we suggest that the presence of a lymphocytic infiltrate should prompt a careful search for other features of malignancy. Other features examined, including elongation of rete ridges, pattern of melanocyte distribution at the dermo-epidermal junction, dermal sclerosis, and pigment in the stratum corneum or in the dermis, were seen in both naevi and melanomas and were not found to be useful in distinguishing benign from malignant lesions.     

A sequential study of the bovine tuberculin reaction.

The sequential histopathological and immunocytochemical changes that characterize the tuberculin reaction were studied in 13 cattle experimentally sensitized to Mycobacterium bovis, and 14 cattle naturally infected with M. bovis. There were two distinct, temporally related patterns of morphological change that were similar for both groups of cattle. The first phase, between 6 hr and 24 hr after the intradermal injection of purified protein derivative (PPD), was characterized by a perivascular aggregation of WC1+ gamma delta T cells and neutrophils and the presence of leucocytoclastic vasculitis within the papillary dermis. The second phase of the reaction was characterized by increased numbers of infiltrating BoCD4+ cells, BoCD8+ cells and macrophages, as well as an increase in expression of the interleukin-2 (IL-2) receptor and the ACT2 antigen. Macrophages were the most numerous infiltrating leucocytes between 24 hr and 72 hr after the intradermal injection of PPD. At 72 hr, the reaction was characterized by intense perivascular cuffing with BoCD4+ cells, BoCD8+ cells and macrophages; gamma delta T cells and neutrophils were a minor component of the reaction and leucocytoclastic vasculitis was no longer observed. No B cells were detected in the dermis throughout the period of study. The increase in skin thickness was primarily because of inflammatory oedema that was contained within the area by a meshwork of fibrin deposited around the collagen bundles of the reticular dermis.     

Malignant melanoma in stasis dermatitis

Two cases of malignant melanoma arising in established stasis dermatitis are described. One case was clinically thought to be melanocytic whereas the other was not. Histologically, both showed similar features with background varicose change of epidermal atrophy, sloughing of the epidermis, intense proliferation of small thick walled blood vessels, lymphocytic infiltrate and dermal fibrosis. In the superficial aspects of the biopsies there was little clue to the diagnosis of melanoma. In the deeper aspects of case 1, groups of melanocytes were present in the reticular dermis which mimicked benign naevus cells. S-100 protein staining confirmed the melanocytic nature of these lesions, their extent and the epidermal involvement. The latter features supported a malignant diagnosis. These lesions can be overlooked clinically as well as histologically.     

Light and electron microscopic features of tropical ulcer.

The histopathological features of 20 tropical ulcers with the electron microscopic findings on seven biopsy specimens are reported. The main findings were loss of epidermis associated with extensive dermal oedema, infiltration by polymorphonuclear leucocytes, and disruption of collagen bundles. The presence of micro-organisms at the site of tissue damage was shown and compared with the morphology of the organisms grown in culture. The most commonly identified bacteria were pleomorphic rods whose electron microscopic appearances accorded most closely with Fusobacteria grown in vitro. Spirochaetes, identified ultrastructurally as Treponema sp, were also present. There was no evidence of vasculitis to explain the rapid onset of ulceration, but necrotic changes seen in the dermis and the inflammatory cell infiltrate suggest that, associated with cell necrosis, bacteria previously shown in vitro have an important role in the pathogenesis of tropical ulcers.     

Immunohistochemical Expression of Perforin in Lichen Planus Lesions

Abstract

Background: Lichen planus (LP) is a chronic inflammatory papulosquamous skin disease characterized by epidermal basal cell damage and a particular band-like infiltrate predominantly of T cells in the upper dermis. It is characterized by the formation of colloid bodies representing apoptotic keratinocytes. The apoptotic process mediated by CD8+ cytotoxic T lymphocytes and natural killer cells mainly involves two distinct pathways: the perforin/granzyme pathway and the Fas/FasL pathway. So far, little is known regarding the role of perforin-mediated apoptosis in LP.

Aim: Is to study the expression and distribution of perforin in the epidermis and dermis of lesional LP skin.

Materials and methods: Skin biopsy specimens from lesional skin of 31 patients with LP and 10 healthy persons were analyzed by immunohistochemistry.

Results: Significant accumulation of perforin?+?cells was found in both epidermis and dermis of LP lesions compared with healthy skin. Perforin expression was significantly upregulated in the epidermis of LP lesions.

Conclusion: Accumulation of perforin?+?cells in the epidermis of LP lesions suggest a potential role of perforin in the apoptosis of basal keratinocytes.     

Immune Cells Are Required for Cutaneous Ulceration in a Swine Model of Chancroid

Cutaneous lesions of the human sexually transmitted genital ulcer disease chancroid are characterized by the presence of intraepidermal pustules, keratinocyte cytopathology, and epidermal and dermal erosion. These lesions are replete with neutrophils, macrophages, and CD4(+) T cells and contain very low numbers of cells of Haemophilus ducreyi, the bacterial agent of chancroid. We examined lesion formation by H. ducreyi in a pig model by using cyclophosphamide (CPA)-induced immune cell deficiency to distinguish between host and bacterial contributions to chancroid ulcer formation. Histologic presentation of H. ducreyi-induced lesions in CPA-treated pigs differed from ulcers that developed in immune-competent animals in that pustules did not form and surface epithelia remained intact. However, these lesions had significant suprabasal keratinocyte cytotoxicity. These results demonstrate that the host immune response was required for chancroid ulceration, while bacterial products were at least partially responsible for the keratinocyte cytopathology associated with chancroid lesions in the pig. The low numbers of H. ducreyi present in lesions in humans and immune-competent pigs have prevented localization of these organisms within skin. However, H. ducreyi organisms were readily visualized in lesion biopsies from infected CPA-treated pigs by immunoelectron microscopy. These bacteria were extracellular and associated with necrotic host cells in the epidermis and dermis. The relative abundance of H. ducreyi in inoculated CPA-treated pig skin suggests control of bacterial replication by host immune cells during natural human infection.     

Differentiation of interdigitating reticulum cells and Langerhans cells in the human skin with T-lymphoid infiltrate. An immunocytochemical and ultrastructural study

The differentiation of two types of T-lymphocyte accessory cells, i.e., interdigitating reticulum cells and Langerhans cells, was studied immunocytochemically and ultrastructurally on cutaneous lesions from patients with mycosis fungoides, a neoplasm of mature T-lymphocytes. In such a condition the lymphoid infiltrate creates, adjacent to the epidermis, a microenvironment in the dermis similar to that of T-cell areas of lymphoid organs. Immunocytochemistry revealed that CD11c+ CD1a- putative monocytic cells co-exist with CD11c+ CD1a+ putative mature accessory cells. By electron microscopy, large numbers of interdigitating reticulum cells in the dermal infiltrate and Langerhans cells in the epidermis were found. Furthermore, monocytes were frequently observed, at times with cells showing intermediate features between monocytes and interdigitating reticulum cells on the one hand and Langerhans cells on the other. In the absence of proliferative phenomena of the above cells, it is conceivable that both interdigitating reticulum cells and Langerhans cells originate from locally migrated monocytes. A possible role of the local tissue micro-environment--namely the T-lymphoid microenvironment for interdigitating reticulum cells and the epidermal microenvironment for Langerhans cells--in inducing the differentiation of monocytes into the two kinds of accessory cells is proposed.     

Systemic dissemination and cutaneous damage in a mouse model of staphylococcal skin infections

Serious staphylococcal infections frequently begin in the skin. The present study used a mouse model of such infections to evaluate the ability of Staphylococcus aureus to disseminate from the skin and to determine if cutaneous damage from the infections was required for dissemination. The mice were inoculated with S. aureus onto flank skin prepared by a tape-stripping method that caused minimal disruption of the epidermal keratinocyte layers. After these inoculations the staphylococci were found to disseminate to the spleen and kidneys of almost all animals within 6 h. Induction of leucopenia did not affect this process. Cutaneous damage was prominent in these experimental infections and included loss of the epidermis, neutrophil infiltration into the epidermis, and complete necrosis of the dermis. The latter also occurred in cyclophosphamide-treated animals, indicating that the organisms themselves and not the host inflammatory responses were responsible. Dermal necrosis did not develop until 48 h after inoculation, a time by which dissemination had already occurred. Therefore, in this mouse model system S. aureus is capable of penetrating the epidermal keratinocyte layers and disseminating rapidly after inoculation; the experimental infections do produce significant dermal damage, but the latter develops after dissemination has already taken place.