Histological increase in inflammatory infiltrate in sun-exposed skin of female subjects: the possible involvement of matrix metalloproteinase-1 produced by inflammatory infiltrate on collagen degradation

To investigate morphological changes occurring during cutaneous photoageing, a correlation between the number of infiltrating cells in the dermis and the degree of collagen damage was examined using sections from clinically normal chronically sun-exposed and sun-protected skin of Japanese female subjects. Haematoxylin and eosin-stained sections from 134 sun-exposed (subjects aged 3-82 years) and 73 sun-protected (subjects aged 1-86 years) areas demonstrated a predominant lymphoid cell and to a lesser extent histiocyte infiltration. The mean +/- SD number of lymphoid cells and histiocytes in the sun-exposed skin sections (427.0+/-192.2 and 147.8+/-83.3 cells/mm2, respectively) was significantly higher than in the sun-protected skin sections (292.6+/-98.3 and 125.9+/-59.0 cells/mm2, respectively) (P < 0.001 and P < 0.05, respectively), and the number of lymphoid cells in the sun-exposed skin sections increased significantly with age up to 50 years (r = 0.400, P < 0.001). Sun-exposed skin sections with severe collagen degeneration had a significantly higher number of lymphoid cells than those with slightly degenerated collagen (mean 626.3 vs. 482.4 cells/mm2, P < 0.01). The mean count of mast cells in sun-exposed skin was 202.0 cells/mm2; this did not vary with the age of the subjects or the level of collagen damage. Immunohistochemical studies using 24 frozen sections identified most of the lymphoid cells infiltrating sun-exposed skin as memory T lymphocytes (CD3+, CD4+ and CD45RO+). The number of cells which displayed immunoreactivity to matrix metalloproteinase (MMP)-1 in the sun-exposed skin sections was significantly higher than in the sun-protected skin sections (mean 170.2 vs. 113.6 cells/mm2, P < 0.05). Among these cells were observed CD3 and MMP-1 double-stained T lymphocytes, and T lymphocytes contacting MMP-1-positive cells. These morphological observations suggest that T lymphocytes infiltrating photodamaged skin may play a part in the degeneration and reduction of collagen through MMP-1 activity.     

Immunohistology of skin pathergy reaction in Behçet's disease

Summary The immunophenotypic characteristics of the skin pathergy reaction (SPR) at 48 h in Behçet's disease (BD) were investigated in 12 patients with BD and in five controls. The findings in 11 positive and one negative SPR lesions of patients with BD were evaluated in comparison with those of normal adjacent skin and with the negative pathergy biopsies from the controls. Positive SPR biopsies showed variable epidermal thickening and cell vacuolization, as well as subcorneal pustule formation. In the SPR dermis, a variable dense focal mononuclear cell (MNC) infiltrate was seen around vessels and skin appendages, extending into the deep dermis. The MNC infiltrate was predominantly composed of T lymphocytes and monocytes/macrophages. The majority of the T lymphocytes were CD4⁺, and almost all expressed CD45RO. Approximately half of the infiltrating cells strongly expressed HLA-DR. Neutrophils constituted less than 5% of the infiltrating cells, but were present as clusters of elastase-positive cells at the needle-prick sites. Vessels within the lesion showed marked congestion and endothelial swelling. The endothelial cells expressed ICAM-1 strongly, and E-selectin moderately. VCAM-1 was not expressed on endothelial cells. The basal and mid-epidermal layers of keratinocytes expressed HLA-DR and ICAM-1 strongly, particularly so in areas close to the dermal MNC infiltrates. In negative pathergy biopsies, there were increased numbers of neutrophils and a few small clusters of macrophages and T lymphocytes only at the needle-prick site, and the endothelial cells of vessels close to these areas expressed E-selectin weakly. The immunohistological findings of the SPR appear to indicate an augmented antigen-independent non-specific induction phase of the inflammatory response. Absence of VCAM-1 expression by endothelial cells suggests that direct epidermal injury is the cause of the cutaneous inflammation.     

Increased Fas ligand expression by T cells and tumour cells in the progression of actinic keratosis to squamous cell carcinoma

BACKGROUND: In the counterattack model of tumorigenesis, it has been proposed that tumours develop resistance to attack from Fas ligand (FasL)-expressing cytotoxic T cells by downregulating Fas (immune escape), while at the same time upregulating FasL expression to induce apoptosis in Fas-expressing T cells (counterattack). OBJECTIVES: The aim of this study was to examine Fas and FasL expression on tumour cells and infiltrating T cells during the progression of actinic keratoses (AK), the benign precursor lesion, to squamous cell carcinoma (SCC). PATIENTS AND METHODS: Samples of AK (n = 20) and SCC (n = 20) were collected from immunocompetent patients attending dermatology clinics. Double-label immunohistochemistry was performed on frozen sections using mouse monoclonal antibodies to Fas or FasL, simultaneously with a rabbit polyclonal antibody to either CD3 or cytokeratin, markers of T cells and keratinocytes, respectively. Cell densities and the optical density of tumour Fas expression were measured using image analysis. RESULTS: FasL-expressing T cells were observed in nine of 19 SCCs, compared with three of 20 AKs (P < 0.05). FasL-expressing tumour cells were found in nine of 18 SCCs, compared with only one of 20 AK specimens (P < 0.005). There was no difference in the number of Fas-expressing T cells infiltrating AK and SCC. Fas expression by keratinocytes, measured by optical density, was lower in SCC (range 0.1-40, median 17) compared with AK (range 4-62, median 25) (P < 0.05). CONCLUSIONS: These results suggest that the greater numbers of FasL-expressing T cells infiltrating into SCC compared with AK are targeting Fas-expressing tumour cells. As AK cells progress to SCC, they subvert this T-cell-mediated killing of tumour cells by downregulating their Fas expression (immune escape). Furthermore, tumour cells upregulate their expression of FasL, possibly as a counterattack measure to induce apoptosis in the increased number of tumour-infiltrating T cells. Thus changes in Fas/FasL-mediated interactions between T cells and tumour cells occur during the progression of AK into SCC.     

Predominance of “memory” T cells (CD4+, CDw29+) over “naive” T cells (CD4+, CD45R+) in both normal and diseased human skin

Summary Absolute numbers of CD3+ T lymphocytes and their subpopulations were determined and statistically evaluated in the lesional skin of psoriasis, atopic dermatitis, nummular dermatitis, pityriasis rosea, and lichen planus. Skin sections were divided into horizontal layers and the numbers of CD3+ T cells as well as CD4+ inducer and CD8+ suppressor-cytotoxic T-cell subsets were counted. In addition, absolute numbers of the two subpopulations of inducer T cells, i.e., memory (4B4+ 2H4-) and naive (4B4- 2H4+) were evaluated. Unexpectedly, epidermal infiltration by T cells was highest in psoriasis and lowest in atopic dermatitis. In most cases, this exocytosis was dominated by CD8+ suppressor/cytotoxic T lymphocytes, with a minimal epidermal mean CD4/mean CD8 ratio of 0.04 in pityriasis rosea and a maximum of 0.48 in psoriasis. Inducer T cells within the epidermis were almost exclusively of the 4B4+ 2H4- memory T-cell subpopulation, whereas 4B4- 2H4+ naive T cells were extremely uncommon in lesional epidermis. Similar results were obtained for dermal T cells in all diseases studied, i.e., 4B4- 2H4+ naive T cells were relatively rare. Papillary dermis infiltration by T cells was highest in lichen planus where a mean CD4/mean CD8 ratio of 1.10, the minimum in this comparative study, was obtained. The mean CD4/mean CD8 ratio of the papillary infiltrate was highest in atopic dermatitis (4.12). Our results indicate disease-specific and significantly different infiltration patterns of T-lymphocyte subsets in the chronic inflammatory dermatoses investigated. The predominant presence of the CD4+ 2H4- memory subpopulation of CD4+ T cells in all diseases studied as well as in normal human skin (reported previously) seems to indicate that the skin immune system is rather unidirectional in its increase in this subpopulation of the inducer T-cell subset. This predominance of the memory subpopulation thus indicates that most T cells of normal and diseased human skin are already primed, i.e., have already met their specific ligand in a MHC II context.     

Histopathological and immunohistochemical changes in psoriatic skin during peptide T treatment

Ten patients with plaque-type psoriasis were treated with 2 mg peptide T i.v. for 28 days. Six patients responded with a substantial clinical improvement. Sequential biopsies from skin lesions were taken before, during and after treatment. The histological score (defining the activity of the psoriasis), the epidermal thickness and the number of infiltrating dermal lymphocytes were all reduced in the six patients who responded to the treatment. An increase in the number of CD1⁺ dendritic cells was detected immunohistochemically in the epidermis of the responders. The nonresponders did not display any pronounced changes.     

Lymphocyte subsets in patients with compositae oleoresin dermatitis and increased UVA sensitivity during treatment with azathioprine

Summary Four patients with severe contact dermatitis resulting from compositae oleoresin were found to have increased sensitivity to ultraviolet light. All showed a clear reduction of Leu-3a-positive lymphocytes (T helper/inducer cells) and cells expressing the Ia phenotype in their blood. The numbers of T suppressor/cytotoxic (Leu 2a) lymphocytes, monocytes and B lymphocytes were within the normal range. Treatment with azathioprine (150 mg daily) improved the eczema. The number of Leu-3a-positive lymphocytes normalized during therapy, but the number of Ia-positive cells did not.     

Skin-infiltrating lymphocytes in normal and disordered skin: activation signals and functional roles in psoriasis and mycosis fungoides-type cutaneous T cell lymphoma.

T lymphocytes recruited into the skin can experience several different outcomes. On the one hand, they may be recruited by adhesion molecules and chemoattractants to enter the perivascular space, but never undergo activation. Other T cells undergo activation and further differentiation under the influence of the cutaneous milieu. These activated lymphocytes then coordinate specific and non-specific immune responses characteristic of inflamed tissue. We have explored two models for studying the activation and function of skin infiltrating T lymphocytes (SIL's). In the first model, we have identified a family of Langerhans cell-related professional dendritic antigen presenting cells that exist in the epidermis and dermis of normal skin, atopic skin, and mycosis fungoides skin. These have APC abilities to activate freshly recruited resting blood T cells that are distinct from another family of macrophage-related cells abnormally present in sunburned or psoriatic skin. In the second model, we examined the function of cells that have already been recruited into the skin of patients with psoriasis and mycosis fungoides. Lesional psoriasis and mycosis fungoides T cells exhibited a variety of T cell receptor gene rearrangements, conclusively demonstrating that heterogeneous populations of T lymphocytes exist in inflamed human skin. From psoriasis, clones were identified that were particularly effective at inducing normal keratinocytes to assume "psoriatic" phenotypic features and functions. Thus, lesional psoriatic SIL's could induce HLA-DR, ICAM, and CDw60 on normal keratinocytes. In addition, psoriatic SIL's induced increased keratinocyte proliferation and cytokine profile changes characteristic of psoriatic epidermis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased densities of Langerhans cells in the epidermis of skin tumors

Using OKT6 monoclonal antibody (MCA) and β-specific anti-S-100 protein (S-100β) MCA, the numbers of Langerhans cells (LC) in the epidermis overlying squamous cell carcinoma (SCC), basal cell epithelioma (BCE), dermatofibroma (DF), and in the lesional epidermis of seborrheic keratosis (SK) were investigated. The numbers of LC were significantly increased in the epidermis overlying SCC and in SK. Moreover, significantly more LC were observed in the epidermis overlying SCC than in SK. The increased density of LC in the epidermis overlying SCC may suggest participation and activation of the mononuclear phagocyte system in this neoplasm. In 8 cases of SCC, the subpopulations of infiltrating lymphocytes around the tumor cell nests were analyzed. The ratio of Leu 3a-positive cells/Leu 2a-positive cells ranged from 0.63 to 1.99. This diversity may reflect complicated immunological interaction between the tumors and the hosts.     

Immunological effects of stress in psoriasis

Background Psychological stress causes phenotypic changes in circulating lymphocytes and is regarded as an important trigger of the Th1‐polarized inflammatory skin disease psoriasis. Objective To study the effects of psychological stress on immunological parameters, i.e. membrane molecules relevant to the pathophysiology of psoriasis, especially cutaneous lymphocyte‐associated antigens (CLA) involved in T and natural killer (NK) cells homing in on the skin. Methods The severity of psoriasis was assessed in patients using the Psoriasis Area and Severity Index. Patients with psoriasis (n = 15) and healthy volunteers (n = 15) were exposed to brief psychological stress in the laboratory. In vitro analyses were conducted 1 h before, immediately following and 1 h after stress exposure. Peripheral T‐ and NK‐cell subsets including CD8+ T lymphocytes, CLA+ lymphocytes and lymphocyte function‐associated antigen type 1 (LFA‐1)+ lymphocytes were analysed by flow cytometry. Results We found a significant stress‐induced increase of CD3+ T lymphocytes in patients with psoriasis only. Analyses of T‐cell subsets revealed that this increase was observable for cytotoxic CD8+ T lymphocytes and CLA+ CD3+ lymphocytes. The total number of circulating NK cells (CD16+, CD56+) increased immediately after stress in both groups whereas only patients with psoriasis showed a significant increase in CLA+ NK cells. Conclusions A higher stress‐induced increase of CLA+ T and CLA+ NK cells in the circulation of patients with psoriasis might point to an increased ability of T and NK cells in the presence of psoriasis to home in on the skin during mental stress. Further studies are needed to verify these relationships in more detail and to investigate the time point at which these cells accumulate within lesional skin, and whether or not psychotherapy improves the quality of life of patients with psoriasis and influences stress‐dependent parameters.     

Immunopathogenic characterization of cutaneous inflammation in Behçet’s disease

Background Behçet’s disease (BD) is a recurrent multisystemic inflammatory disease characterized by recurrent oral aphthous and genital ulcers, ocular lesions and cutaneous lesions. Although many studies of cytokine levels in sera of BD patients have been conducted, there are only limited number of studies about the cytokine expression and cellular infiltration in the BD‐related skin lesions. Objectives To investigate the immunophenotypes and cytokine profiles of BD‐related skin lesions. Methods Twenty patients who fulfilled the diagnostic criteria for BD with BD‐related skin lesions were enrolled in this study. We assessed the histopathological features of BD‐related skin lesions by immunohistochemical studies with anti‐human CD4, CD8, CD68, FoxP3, CD‐11b, IFN‐γ and IL‐4 antibodies. Results Immunophenotyping of inflammatory infiltrating cells showed that CD68+ macrophages were the most common type of infiltrated cells in erythema nodosum‐like lesions, erythema multiforme‐like lesions and Sweet’s syndrome‐like lesions, whereas neutrophils were the main population of inflammatory infiltrating cells in papulopustular lesions. In all of the four types of BD‐related skin lesions, the percentage of CD8+ T cells was higher than that of CD4+ T cells (P < 0.05), and IL‐4 expression was stronger than IFN‐γ expression (P < 0.05). Conclusion In this study, we assessed the infiltrating inflammatory cells and cytokine expression of acute cutaneous lesions in BD through immunohistochemical staining of BD‐related skin lesions. Further studies about the disease activity and the molecular biology underlying the cutaneous inflammation are needed to understand the detailed pathogenesis of BD.     

Predominant cutaneous infiltration by OKT6- and OKT8-positive cells in a case of Sézary syndrome

Summary Using an immunoperoxidase (skin biopsy) and an immunofluorescence (peripheral blood, bone marrow punctate) technique, and monoclonal antibodies raised against peripheral mature lymphocytes, T helper subsets, T suppressor subsets, and Langerhans cells, we found a predominant dermal infiltration with lymphocytes of the suppressor phenotype and a predominant epidermal infiltration with Langerhans cells in a patient with Sézary syndrome (cutaneous T-cell lymphoma, CTCL). Repeated peripheral blood examinations showed an increased percentage of lymphocytes of the helper phenotype. A bone marrow examination revealed a ratio of suppressor/helper subsets of 1:4. The findings in the skin seem to be inconsistent with most of the results of previous studies in patients with CTCL; the significance of these findings is discussed.This study was partly supported by the Deutsche Forschungsgemeinschaft, Grant no. Lo 285/2-1This work is dedicated to Prof. Th. Nasemann on occasion of his 60th birthday     

Involvement of granulysin-producing T cells in the development of superficial microbial folliculitis

BACKGROUND: Granulysin is a recently identified antimicrobial protein expressed on cytotoxic T cells, natural killer (NK) cells and NKT cells. It has been shown that granulysin contributes to the defence mechanisms against mycobacterial infection. Superficial microbial folliculitis is a common skin disease. In a previous report, we showed that, as a first line of defence, alpha-defensin, a human neutrophil peptide, and beta-defensin (human beta-defensin-2) were expressed in infiltrating neutrophils and in lesional epidermal keratinocytes, respectively, in superficial folliculitis. As we also observed many infiltrating lymphocytes in lesional dermis, we hypothesized that infiltrating lymphocytes may possess antimicrobial substances, such as granulysin, and play a role in the defence mechanism as a second line of defence. OBJECTIVES: Seven specimens of superficial microbial folliculitis diagnosed clinically and histologically were examined by means of immunohistochemistry. To identify the phenotype of cells expressing granulysin, confocal laser microscopic examination was performed. RESULTS: A dense lymphoid cell infiltrate was observed in pustules, in the perivascular regions. A large number of these lymphoid cells were positive for granulysin. Phenotypically, cells consisted of CD3+ T cells, CD8+ T cells and UCHL-1+ T cells. CD20+ cells and CD56+ cells were not observed. Microscopic examination with a confocal laser showed that the lymphocytes producing granulysin were CD3+ and CD4+ T cells but not CD8+ T cells. CONCLUSIONS: We showed that many granulysin-bearing T cells infiltrated affected follicles and perilesional dermis in superficial microbial folliculitis. However, few granulysin-positive lymphoid cells were observed in sterile pustular lesions. Our observations indicated that adaptive immunity such as granulysin, a lymphocyte-produced antimicrobial protein, may play an important role in the cutaneous defence mechanism.     

Induction of skewed Th1/Th2 T-cell differentiation via subcutaneous immunization with Freund's adjuvant

CD4+ T cells differentiate into at least two distinct subsets, Th1 and Th2, that are characterized by their cytokine-producing profiles. In this study, we attempted to delineate whether and how CD4+ T-cell responses could be skewed in one direction or another. BALB/c mice were immunized with chicken ovalbumin (OVA) emulsified with either incomplete or complete Freund's adjuvant (IFA or CFA). When lymph node cells were assessed on day 7, antigen specific proliferation was similarly observed both in the mice immunized with IFA and CFA. In contrast, on day 28 there was a less significant response in the mice primed with IFA than in those primed with CFA. ELISA analyses revealed more Th1 predominant cytokine production by T cells immunized with OVA+CFA rather than in IFA, which resulted in balanced IFN-gamma and IL-4 production. Flow cytometric analyses of intracellular cytokines confirmed that T cells from mice primed with CFA produced Th1 cytokines more predominantly. When lymph node dendritic cells (DC) were compared for their co-stimulatory molecule expression, priming with CFA and IFA similarly upregulated CD80 and CD86 expression by lymph node DC, and no significant differences were observed in CD40, 54, 80 and 86 expression between the DC harvested from IFA and CFA immunized mice. In addition, both priming with IFA and CFA similarly induced IL-12 production by DC. Thus, although the reason(s) for the preferential induction of a Th1/Th2 response remains unknown, these results indicate that a relatively Th1/Th2 skewed response is differentially induced by different types of adjuvants, and induction of a Th1 skewed response may be responsible for long lasting cellular immunity.     

Immune-associated cells in basal cell carcinomas of skin

Increased numbers of mast cells (MCs) and lymphocytes infiltrating in basal cell carcinomas (BCCs) have been observed. The presence of these infiltrating cells has been considered a sign of an immunologic anti-tumor response in the host, but the relationship of these two cell populations has not been examined. To elucidate this possible relationship, 30 non-ulcerated BCCs were analyzed. Frozen sections of the tumors were stained with monoclonal antibodies for Langerhans' cells, lymphocyte subsets and natural killer cells. Fluorescein isothiocynate (FITC) -aviclin as well as anti-tryptase and anti-CD45RO monoclonal antibodies were used on formalin-fixed, paraffin-embedded secdons for mast cell and T cell identification, respectively. B cells and natural killer cells were rarely observed in these tumors. MCs and T cells were quantified by direct enumeration and expressed as number of cells per high power field (hpf). FITC-avidin and anti-tryptase antibodies were equivalent in their ability to identify MCs. MC content in BCCs ranged from 1.0 to 31 cells/hpf. The number of T cells ranged from 0 to 50 cells/hpf with helper/suppressor cell ratios of 0.2 to 10. There was no correlation between helper/suppressor ratios and mast cell numbers; however, an inverse relationship was observed between the numbers of T cells and the number of mast cells in these tumors. These studies indicate that T cells and MCs are the primary immune cell populations responding to BCCs, and that decreased numbers of T cells are associated with more aggressive tumors.     

Increased expression of the natural killer cell inhibitory receptor CD94/NKG2A and CD158b on circulating and lesional T cells in patients with chronic plaque psoriasis

BACKGROUND: Psoriasis is a common inflammatory cutaneous disorder characterized by activated T-cell infiltration. T lymphocytes bearing natural killer cell receptors (NKRs) have been suggested to play an important role in the pathogenesis of psoriasis. However, the expression pattern of activating and inhibitory NKRs on T lymphocytes from psoriatic patients and its significance in psoriasis needs further study. OBJECTIVES: To investigate the pathogenesis of NKR-expressing T cells in psoriasis. MATERIALS AND METHODS: Thirty patients with chronic plaque psoriasis and 20 healthy controls were enrolled in this study. The immunophenotypic profiles of NKRs, including CD56, CD16 (activating NKRs), CD158a, CD158b, CD94 and NKG2A (inhibitory NKRs), were analysed in peripheral blood T lymphocytes, as well as psoriatic lesional infiltrating T cells, by triple-fluorescence flow cytometry. RESULTS: A significant increase of inhibitory CD8+ CD158b+, CD4 CD8 CD158b+ and CD8+ CD94/NKG2A+ T cells was found in the peripheral blood of patients with psoriasis when compared with controls. Tissue-infiltrating T lymphocytes expressing inhibitory receptors CD158b, CD94 and NKG2A were found in psoriatic lesions. There was a significant positive correlation between the increased percentage of circulating CD8+ CD94/NKG2A+ T cells and the Psoriasis Area and Severity Index. CONCLUSIONS: In the present study, we demonstrated increased proportions of particular subsets of inhibitory CD158b+ and/or CD94/NKG2A+ T cells in patients with psoriasis. The elevation of these inhibitory NKR-expressing T cells was correlated with disease severity, which may signify the possibility of chronic antigen-driven stimulation and dysregulated cytokine production in the pathogenesis of psoriasis.     

Inflammation in acne scarring: a comparison of the responses in lesions from patients prone and not prone to scar

BACKGROUND: Many patients with inflammatory acne suffer from significant scarring, which is disfiguring and difficult to treat. A cell-mediated immune response is considered to be involved in the pathogenesis of acne, although the extent of this response has been found to differ among patients. OBJECTIVE: To assess whether there were differences in the cell-mediated immune responses at different time points in inflamed lesion development and resolution in patients who were prone (S patients) and those with the same degree of inflamed acne who were not prone (NS patients) to develop scarring. METHODS: Cellular and vascular markers were investigated using standard immunohistochemical techniques on biopsies of inflamed lesions of known duration, i.e. < 6 h (n = 14), 24 h (n = 14), 48 h (n = 10), 72 h (n = 10) and 6-7 days (n = 11) from the backs of acne patients. RESULTS: In early lesions from NS patients there was a large influx of CD4+ T cells, macrophages and Langerhans cells with a high number of cells expressing HLA-DR. Also there was significant angiogenesis and vascular adhesion molecule expression. Cell recruitment peaked in 48 h lesions, after which leucocyte numbers decreased and vascular activity returned to normal. Of the T cells, only 50% were memory/effector (CD45RO+) and naive (CD45RA+) cells, while the remainder were unclassified (CD45RO-, CD45RA-). In early lesions from S patients, CD4+ T cell numbers were smaller, although a high proportion were skin homing memory/effector cells. Langerhans cell numbers and cellular HLA-DR expression were low, while numbers of macrophages, blood vessels and vascular adhesion molecules were high. In resolving lesions angiogenesis remained high, with a further influx of macrophages and skin homing memory/effector cells and increased cellular HLA-DR expression. CONCLUSIONS: The cellular infiltrate was large and active with a greater nonspecific response (few memory T cells) in early lesions of NS patients, which subsided in resolution. In contrast, a predominantly specific immune response was present in S patients, which was initially smaller and ineffective, but was increased and activated in resolving lesions. Such excessive inflammation in healing tissue is conducive to scarring and suggests that the use of topical anti-inflammatory treatments would be appropriate for these patients.     

Allergic contact dermatitis: the cellular effectors

Contact hypersensitivity reactions are mediated by lymphocytic effector cells. Until recently it was believed that the most important of these were CD4+ T lymphocytes. However, there is growing evidence that in many instances the predominant effector cell may be a CD8+ T lymphocyte, with in some instances CD4+ cells performing a counter-regulatory function. Here we review the roles of CD4+ T helper (Th) cells and CD8+ T cytotoxic (Tc) cells, and their main functional subpopulations (respectively, Th1 and Th2 cells and Tc1 and Tc2 cells) in the elicitation of contact hypersensitivity reactions and consider the implications of effector cell selectivity for the biology of allergic contact dermatitis.     

CD1a+, CD3+, CD4+, CD8+, CD68+ and cutaneous lymphocyte-associated antigen-positive cells in Bowen's disease

BACKGROUND: Bowen's disease (BD) is a squamous cell carcinoma in situ that rarely invades into the underlying dermis. However, little is known about its immunohistology. Objectives To evaluate the relationship between the cytological properties of the tumour cells in BD and the host immune response. METHODS: We examined the expression of p53, proliferating cell nuclear antigen (PCNA) and Ki67 antigen, and the number of mitotic cells, together with the number of intratumoral and dermal infiltrating CD1a+, CD3+, CD4+, CD8+, CD68+ and cutaneous lymphocyte-associated antigen (CLA)+ cells in 18 cases of genital BD. RESULTS: When compared with normal genital skin (n = 10), there was a significantly higher number of mitotic cells as well as higher expression of p53+, PCNA+ and Ki67+ cells in BD. There was significant mutual correlation between CD3+, CD4+ and CD68+ cells in the tumoral epidermis. The number of CD1a+ Langerhans cells significantly decreased in BD epidermis; however, dermal CD1a+ cells were increased. Interestingly, numbers of dermal CD1a+ cells significantly correlated with those of intratumoral CD3+, CD4+ and CD68+ cells. In situ hybridization for human papillomavirus (HPV) demonstrated that HPV-infected BD had significantly less infiltration of intratumoral CD3+ cells and CLA+ cells. CONCLUSIONS: The present data suggest that dermal CD1a+ cells may participate in the immune surveillance and that HPV infection may interfere with the intratumoral infiltration of CLA+ cells in BD.     

Lymphocytes and Langerhans cells in patch tests

The distribution of immunocompetent cells was analysed in allergic (nickel) and irritant (dithranol) patch tests using conventional transmission electron microscopy and labelling with monoclonal antibodies in an avidin-biotin immunoperoxidase study. The biopsies were taken 24 or 48 h after the allergen/irritant application. In allergic and irritant reactions, most inflammatory cells were OKT11 positive (pan T lymphocytes). The majority of these cells were also OKT4 positive (helper/inducer T lymphocytes), while the minority were OKT8 positive (suppressor/cytotoxic T lymphocytes). NK9 positive cells (natural killer cells) were observed in small numbers. The number of dendritic OKT6 and OKIal positive cells (Langerhans cells) in the epidermis was unaffected in allergic reactions. In irritant reactions, a normal number of OKT6 positive Langerhans cells was observed, while the number of OKIal positive cells had increased in the epidermis. Dithranol caused prominent fine structural changes in the mitochondria of the Langerhans cells, while the keratinocytes appeared largely unaffected. The present study indicates that allergic and irritant patch tests cannot be differentiated reliably using current immunohistopathological or electron microscopic techniques, in spite of the small differences observed.     

Increased expression of an epidermal stem cell marker, cytokeratin 19, in cutaneous squamous cell carcinoma

Background Cytokeratin 19 (CK19) has been considered to be a putative marker for epidermal stem cells in the hair follicle bulge. Cumulative reports have shown that epidermal stem cells play an important role in skin carcinogenesis. However, to date there has been no report on the clinical alteration of the stem cells in squamous cell carcinoma (SCC). Objectives To investigate alteration of the stem cells and proliferating cells and to assess their relationship and potential contribution to SCC. Methods Thirty paraffin‐embedded neoplastic skin lesions, consisting of 10 cases each of actinic keratosis (AK), Bowen disease (BD) and SCC, were examined immunohistologically for CK19 and Ki‐67. Results Positive reactivity for CK19 was seen in 30% of AK, 50% of BD and 80% of SCC lesions. There was significantly higher expression levels of CK19 in SCC than in AK and BD (P < 0·05). In addition, BD lesions harboured a significantly higher number of CK19‐positive cells than did AK lesions (P < 0·05). There were significant differences in Ki‐67 labelling indices between AK and BD and between AK and SCC (P < 0·001), but not between BD and SCC (P > 0·05). Furthermore, a serial section comparison study showed that there was a minor population of cells co‐expressing CK19 and Ki‐67 in a subset of the tumour cells of SCC samples. The percentage of CK19+ cells significantly correlated with that of Ki67+ cells in all examined neoplastic skin lesions. Conclusions These results suggest that CK19 expression may be associated with the retention of stem cell characteristics or a state that is uncommitted to terminal squamous differentiation.