Ultrastructural documentation of HLA-DR antigen reactivity in normal human acrosyringial epithelium

Psoriasis in HIV infection: an update

Psoriasis is a prevalent systemic immune-mediated disease with cutaneous manifestations. In HIV-infected patients, psoriasis may have a higher incidence, present atypical and more exuberant clinical features, and is frequently recalcitrant to treatment. Despite this aggravated severity, treatment options for psoriasis in HIV-infected individuals remain limited due to the risk of fatal immunosuppression associated with both classical immunosuppressants and new biological drugs. Notwithstanding, drug therapy in psoriasis has been undergoing major advances for the last few years, with novel drugs approved, which could significantly add to the management of HIV-infected patients. It is therefore our aim to present a review of the available literature to highlight the updated evidence on psoriasis in HIV-infected individuals, particularly in regards to its epidemiology, proposed pathophysiology, clinical presentation, currently available therapeutic options, and future perspectives.

Facts, fallacies, fears, and frustrations with human pheromones

Among primates in general, pheromones are of variable importance to social communication. Data on humans have generated the greatest controversy regarding the existence of pheromonal communication. In this review, the likelihood of pheromonal communication in humans is assessed with a discussion of chemical compounds produced by the axilla that may function as pheromones; the likelihood that the vomeronasal organ (VNO), a putative pheromone receptor organ in many other mammals, is functional in humans; and the possible ways pheromones operate in humans. In the human axilla, the interactions between the cutaneous microflora and axillary secretions render this region analogous to scent glands found in other primates. Both the chemistry of axillary secretions and their effects on conspecifics in humans appear to be analogous to other mammalian pheromone systems. Whichever chemical compounds serve a pheromonal function in humans, another unknown is the receptor. Although the VNO has been implicated in the reception of pheromones in many vertebrates, it is not the only pathway through which such information has access to the central nervous system; there is ample evidence to support the view that the olfactory epithelium can respond to pheromones. Furthermore, if a chemical activates receptors within the VNO, this does not necessarily mean that the compound is a pheromone. An important caveat for humans is that critical components typically found within the functioning VNO of other, nonprimate, mammals are lacking, suggesting that the human VNO does not function in the way that has been described for other mammals. In a broader perspective, pheromones can be classified as primers, signalers, modulators, and releasers. There is good evidence to support the presence of the former three in humans. Examples include affects on the menstrual cycle (primer effects); olfactory recognition of newborn by its mother (signaler); individuals may exude different odors based on mood (suggestive of modulator effects). However, there is no good evidence for releaser effects in adult humans. It is emphasized that no bioassay-guided study has led to the isolation of true human pheromones, a step that will elucidate specific functions to human chemical signals.

Application of Staphylococcal enterotoxin B on normal and atopic skin induces up-regulation of T cells by a superantigen-mediated mechanism

BACKGROUND

The skin of patients with inflammatory skin diseases such as atopic dermatitis is frequently colonized with Staphylococcus aureus. Colonization with S aureus has been reported to exacerbate atopic dermatitis. Recent studies have demonstrated that S aureus isolated from the skin of patients with atopic dermatitis releases bacterial toxins that act as superantigens. We have previously applied the staphylococcal superantigen staphylococcal enterotoxin B (SEB) on intact human skin and found that the application led to induction of dermatitis.

OBJECTIVE

The purpose of the study was to determine whether superantigen-induced dermatitis is primarily due to a T cell-superantigen-mediated reaction or represents nonspecific cytokine-driven inflammation.

METHODS

We applied SEB, vehicle, and sodium lauryl sulfate on normal skin in healthy (n = 6) and atopic subjects (n = 6) and biopsy specimens were taken from all treated areas. The biopsy specimens from all subjects and peripheral blood from the atopic subjects were analyzed for the T-cell receptor (TCR) Vbeta repertoire with mAbs against TCR Vbeta 2, 3, 8.1, 12, 14, and 17.

RESULTS

From all subjects, both healthy and patients with atopic dermatitis, skin biopsy specimens from SEB-treated areas demonstrated selective accumulation of T cells expressing SEB-reactive TCR Vbeta 12 and 17 (P <.05). This selective up-regulation was not found in the sodium lauryl sulfate-treated areas.

CONCLUSION

Our data strongly support that superantigen-induced T-cell activation is involved in the dermatitis seen after experimental application of SEB on intact skin.

Localization of rabbit huntingtin using a new panel of monoclonal antibodies

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG repeat which is expressed as a polyglutamine tract near the N-terminus of the gene product, huntingtin. N-terminal huntingtin fragments form intranuclear aggregates in HD patients and these may be involved in the pathogenesis. Monoclonal antibodies (mAbs) against three different regions of huntingtin (amino acids 997-1276, 1844-2131 and 2703-2911) have been produced and two of the epitopes have been identified using phage displayed peptide libraries. All mAbs reacted with 350 kDa huntingtin on Western blots and one mAb from each region was selected for further study by strong immunoreactivity with neurons in different regions of rabbit brain and by ability to immunoprecipitate native huntingtin. Subcellular fractionation and sucrose density centrifugation of rabbit brain extract showed that most of the huntingtin exists as a high molecular weight complex in the cytoplasm. Two outstanding problems have been addressed; the location of huntingtin in tissues outside the central nervous system and whether huntingtin is present in the nucleus of normal cells. We conclude that huntingtin is present at low levels in most non-neuronal cells though we have identified an interstitial cell type in skin with very high immunoreactivity. Using both immunolocalization and nuclear purification methods, we were unable to exclude the possibility that a small proportion of full-length huntingtin is present in the nucleus.

Distribution of interferon-gamma receptors in normal and psoriatic skin

Recent data suggest that imbalances in production and secretion of cytokines, in particular interferon-gamma (IFN-gamma), may be crucial in the pathogenesis of psoriasis. In order to exert its role on target cells, IFN-gamma has to interact with a specific cell membrane receptor termed the IFN-gamma-receptor (IFN-gamma R). We studied the distribution of IFN-gamma Rs in frozen skin biopsies from 25 psoriatics and 5 normal controls with two unrelated monoclonal antibodies, and compared its distribution with that of the IFN-gamma-inducible HLADR- and ICAM-1 antigens. In normal skin, IFN-gamma Rs were restricted to the basal cell layer; weak staining was found on scattered mononuclear cells in the papillary dermis. In 13/25 active psoriatic lesions, additional suprabasal immunoreactive foci, and in 5/25 cases, diffuse immunoreactivity of the entire epidermis were seen. No striking topographical similarities between the site and number of IFN-gamma R+, HLADR+ and ICAM-1+ keratinocyte foci were observed, suggesting that cytokines other than IFN-gamma induce HLADR-antigens on psoriatic keratinocytes in vivo. The restricted distribution of IFN-gamma R on the germinative cell layer in normal skin confirms the role played by IFN-gamma in the normal growth regulation of the epidermis. The de novo suprabasal expression of IFN-gamma R in psoriasis argues against the current hypothesis that IFN-gamma R are down-regulated due to a local excess of IFN-gamma or transforming growth factor alpha (TGF-alpha). Whether IFN-gamma Rs in psoriatic skin are functionally normal and involved in signal transmission, remains to be studied.

Modulation of interferon-gamma-induced HLA-DR expression on the human keratinocyte cell line SCC-13 by ultraviolet radiation

Cell surface expression of major histocompatibility determinants on epidermal keratinocytes is a characteristic feature of a number of inflammatory dermatoses and in all likelihood is caused by diffusion of human leukocyte antigen (HLA)-DR-inducing cytokines from cells present in the dermal mononuclear cell infiltrate. Many of these same disorders respond to ultraviolet (UV) radiation phototherapy. Using the human SCC-13 keratinocyte cell line as a model, UV radiation was found to inhibit interferon-gamma-induced HLA-DR expression. Inhibition correlated closely with decreased steady-state levels of HLA-DR mRNA. These findings provide evidence that the therapeutic effect of UV radiation phototherapy may be mediated by its capacity to down-regulate cytokine-induced keratinocyte HLA-DR expression.

1 alpha,25-dihydroxyvitamin D3 modulates Ia antigen expression induced by interferon-gamma and prostaglandin E2 production in Pam 212 cells

Recent investigations suggest that 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] has an effect on the regulation of immune responses and that keratinocyte (KC) expression of major histocompatibility complex class II antigens may be involved in immune responses. We investigated the modulation by 1 alpha,25(OH)2D3 of Ia antigen expression induced by interferon-gamma (IFN-gamma) and prostaglandin E2 (PGE2) production in Pam 212 cells. 1 alpha,25(OH)2D3 at 10(-6), 10(-8) or 10(-10) M significantly decreased the levels of IFN-gamma-induced Ia antigen expression in Pam 212 cells. Pam 212 cells produced PGE2 and 1 alpha,25-(OH)2D3 enhanced Pam 212 cell PGE2 production. However, indomethacin (1, 5 and 10 micrograms/ml) did not abrogate the inhibitory effect of 1 alpha,25(OH)2D3 on IFN-gamma induction of Ia antigen expression in Pam 212 cells, indicating that the products of the cyclo-oxygenase pathway do not mediate 1 alpha,25(OH)2D3 inhibition of IFN-gamma induction of Pam 212 cell Ia antigen expression. Our studies suggest that in Pam 212 cells the levels of Ia antigen expression induced by IFN-gamma and PGE2 production are negatively and positively regulated by 1 alpha,25(OH)2D3, respectively, and that 1 alpha,25(OH)2D3 may play a role in the regulation of immune responses.

Immune-associated surface markers of human keratinocytes

The results of a number of investigations have proved that human keratinocytes (HKs) possess the ability to synthesize and express cell surface moieties characteristic of effector and/or accessory cells of the immune system. The present paper summarizes the known immune cell surface features of HKs, reflecting their stage of activation and differentiation. The surface and functional characteristics of HKs suggest their monocyte/macrophage behavior, which fits in well with the presumed active involvement of HKs in the skin immune system.

Expression of T6 antigen on keratinocytes in alopecia areata

The expression of T6 antigen within hair follicles in alopecia areata was studied using the APAAP technique (alkaline phosphatase monoclonal anti-alkaline phosphatase method). Scalp biopsies were taken from 15 subjects with alopecia areata, nine in an active stage and 6 in a stationary stage of the disease. Six-micrometer-thick frozen sections were stained with OKT6 antiserum. OKT6 are monoclonal antibodies raised against human thymocytes; they cross-react with epidermal Langerhans cells and are a highly specific marker. Nine of the specimens displayed T6 staining on keratinocytes in the bulb matrix, and all nine were from the subjects presenting the active stage of disease. The specimens from the other six biopsies, from subjects in a stationary stage, did not show T6 staining of bulbar keratinocytes. Moreover, in four of the active-stage cases we found T6 staining also on epidermal keratinocytes.

Antigenic profile of human acrosyringium

The demonstration of HLA-DR on human acrosyringium has led to the suggestion that eccrine epithelium, through its interaction with certain molecules, might play an active role in epidermal immune responses. An immunohistochemical study was undertaken to identify the antigenic profile of acrosyringium in normal skin and following the intradermal administration of a T-lymphocyte-derived cytokine, interferon gamma (IFN-gamma). Acrosyringium in normal skin, in contrast to interappendageal epidermis, was found to lack CD1a+ Langerhans cells. However, antigens CD36 (OKM5) and L1 (MAC387) were uniquely expressed by keratinocytes immediately adjacent to the distal portion of acrosyringium. Constitutive expression of each class II MHC antigen, namely HLA-DR, DP and DQ was observed on luminal acrosyringial cells. EMB11 antigen (CD68), a mononuclear cell determinant, was similarly expressed on acrosyringial epithelium in normal skin. Following intradermal administration of IFN-gamma, intercellular adhesion molecule-1 (ICAM-1) (CD54) was induced on acrosyringial epithelium and the expression of HLA-DR was intensified. A range of other markers including CD3, CD4, CD8, CD11a, CD11b and CD15 were not expressed by acrosyringium either in normal skin or after administration of IFN-gamma. Expression of antigens associated with cell-mediated immune mechanisms on acrosyringium is consistent with the hypothesis that it may have an immunological role in epidermal immune responses.

Altered expression of major histocompatibility complex (MHC) antigens by epidermal tumours

Alteration in the major histocompatibility complex (MHC) antigen expression by cutaneous tumours may enable them to escape host defence mechanisms and to invade surrounding tissue. Immunohistochemical studies in a wide range of epidermally derived tumours demonstrated expression by keratinocytes of the class II molecule HLA-DR in squamous cell carcinoma (SCC) (2 of 8 cases) and keratoacanthoma (KA) (2 of 7 cases). Additionally, HLA-DP and DQ were expressed by single cases of SCC and KA, although, unlike the widespread distribution of DR, DP and DQ, were only present on keratinocytes adjacent to the inflammatory infiltrate. Therefore, keratinocytes in cutaneous tumours, like carcinoma cells of the colon and breast, may express class II MHC antigens during tumour growth. Beta-2-microglobulin (B2M), an invariant MHC class I marker, was absent in all cases of basal cell carcinoma. Variable loss of B2M was observed in squamous cell carcinoma, Bowen's disease and actinic keratoses, suggesting reduced B2M expression by dysplastic cells. However, the variability in B2M staining both between and within diagnostic categories restricts it's immunodiagnostic usefulness.

Human epidermal T cells predominantly belong to the lineage expressing alpha/beta T cell receptor

The epidermis of clinically normal-appearing human skin harbors a phenotypically heterogeneous population of T lymphocytes (TCs), the majority of which are CD2+/CD3+/CD5+ "memory" cells, but in an unactivated state, and express the TCR-alpha/beta. In contrast to murine skin, only a very minor subpopulation of CD3+ cells in the human epidermis bears the TCR-gamma/delta. Epidermal TCs primarily are distributed along the rete ridges in the basal keratinocyte layer and are often in close apposition to Langerhans cells (LCs). These TCs were propagated from epidermal cell suspensions after stimulation with TC activating agents (Con A, rIL-1, rIL-2), then evaluated for phenotypic features and TCR diversity. Similar to the in situ situation, most were CD4-/CD8+/TCR-alpha/beta+. In addition, two cultures contained TCR-gamma/delta+ cells; one of these determined to be an adherent CD4-/CD8+ population. Epidermal TCs were significantly (p less than 0.0001) more abundant in the sole than in the other body regions examined (i.e., 40 vs. 7 CD3+ cells/linear centimeter of epidermis) and seemed to have a particular affinity for the acrosyringial epithelium of eccrine sweat ducts. Moreover, the sole usually contained a greater number of CD8+ relative to CD4+ TCs, whereas the epidermal CD4/CD8 ratio in the trunk and extremities was quite variable, although the trend also was towards a slightly larger percentage of CD8+ cells. Collectively, our data suggest that the volar epidermis has a unique microenvironment which is responsible for both the higher density of TCs, preferentially CD8+, and lower number of LCs. This study has not only provided evidence for significant regional variability in the human epidermal TC population of normal skin, but also strengthens the concept for skin-associated lymphoid tissues (SALT), whereby memory TCs recirculate back to the epidermis and interact with resident antigen-presenting cells (i.e., LC).

Alterations induced in normal human skin by in vivo interferon-gamma

In a study of the direct effects of interferon-gamma (IFN-gamma) on normal human skin, healthy adult male volunteers received either 3 micrograms (n = 4) or 30 micrograms (n = 9) of recombinant IFN-gamma administered intradermally over 3 days. Biopsies were taken on day 6 and histopathological examination of fixed paraffin-embedded sections from sites which had received 30 micrograms IFN-gamma revealed a moderate perivascular lymphohistiocytic dermal infiltrate with mast cells. Immunophenotyping of 5 microns cryostat sections demonstrated that 3 micrograms IFN-gamma induced keratinocyte HLA-DR expression in the absence of any significant infiltrate. More intense keratinocyte HLA-DR expression was produced by 30 micrograms IFN-gamma in all specimens, with HLA-DP concurrently expressed in three biopsies. The ratio of CD4:CD8 cells within the infiltrate was approximately 3:1. CD1 + cells within the epidermis were markedly depleted by 30 micrograms IFN-gamma, while CD1-labelled cells were observed in the dermal perivascular infiltrate. Intradermal IFN-gamma induces similar immunopathological changes to those observed in many of the inflammatory dermatoses.

Monoclonal antibody MAC 387 recognizes a myelomonocytic antigen shared by epithelial cells in inflammatory skin diseases

The monoclonal antibody MAC 387 recognizes an antigen expressed by human macrophages and granulocytes. Normal epidermis does not react with the antibody, but the inflamed epidermis may react. In this immunocytochemical study we have investigated the intracytoplasmic expression of the MAC 387 antigen in biopsies of a variety of skin disorders. In lichen planus the basal cells were usually negative, whilst suprabasal cells were positive. In the majority of other inflammatory dermatoses studied, there was positive staining of basal and suprabasal cells. A parallel frozen- and paraffin-section study of biopsies of cutaneous T-cell lymphomas and inflammatory conditions failed to demonstrate HLA Class II expression in the cytoplasm of keratinocytes. Expression of the MAC 387 antigen in the epidermis is directly associated with cell-mediated activity in the papillary dermis, but is not related to HLA Class II expression.

Occurrence of Langerhans cells and expression of class II antigens on keratinocytes in malignant and benign epithelial tumors of the skin: an immunohistopathologic study with monoclonal antibodies

We used an avidin-biotin complex immunoperoxidase technique with various monoclonal antibodies to determine Langerhans cell densities, class II antigen expression on keratinocytes, and phenotypes of other infiltrating cells in several malignant and benign epithelial tumors of the skin. Our observations indicate (1) there are few Langerhans cells in nests of basal cell carcinoma and squamous cell carcinoma; (2) there are increased Langerhans cell densities in seborrheic keratoses, verrucous epidermal nevus, and Bowen's disease; (3) there is an expression of class II molecules on the keratinocytes and cancer cells of basal cell carcinoma, squamous cell carcinoma, Bowen's disease, seborrheic keratosis, and verrucous epidermal nevus; and (4) there is a netlike staining of the keratinocyte surface with OKM5 in the epidermal lesion of seborrheic keratosis, verrucous epidermal nevus, and Bowen's disease, as well as in the epidermis adjacent to the basal cell carcinoma and squamous cell carcinoma nests.

Epidermal keratinocytes express the adhesion molecule intercellular adhesion molecule-1 in inflammatory dermatoses

Using indirect immunofluorescence assays on frozen tissue sections of skin from healthy subjects and subjects with inflammatory skin diseases, we found that intercellular adhesion molecule-1 (ICAM-1) was expressed in a cell surface pattern on epidermal keratinocytes at the site of lymphoid infiltration in cutaneous dermatoses. ICAM-1 was not expressed on epidermal keratinocytes in noninflamed skin. Its expression was not related solely to epidermal hyperproliferation, as hyperproliferative, tape-stripped epidermis did not express ICAM-1. We have reported previously that ICAM-1 expression on epidermal keratinocytes was upregulated by treatment with interferon gamma and that activated T lymphocytes bound to cultured epidermal keratinocytes in vitro by lymphocyte function associated-1 (LFA-1) molecules on T cells and ICAM-1 on epidermal keratinocytes. Taken together, these data suggest that upregulation of expression of ICAM-1 is an important feature of cutaneous inflammation.

Characterization of intercellular adhesion molecule-1 and HLA-DR expression in normal and inflamed skin: modulation by recombinant gamma interferon and tumor necrosis factor

Lymphocytes bind to cultured keratinocytes that are treated with interferon gamma (IFN-gamma) and tumor necrosis factor (TNF). When the lymphocytes are preincubated with antibody to lymphocyte function associated antigen-1 (LFA-1), this adherence is inhibited. Because intercellular adhesion molecule-1 (ICAM-1) is a ligand for LFA-1, we studied the cellular expression of ICAM-1, as well as two other IFN-gamma-inducible antigens, (HLA) human lymphocyte antigens DR and DQ, in both normal and diseased skin. The modulation of these cell surface antigens by IFN-gamma and TNF with the use of short-term organ cultures of skin was compared with isolated keratinocytes grown in a conventional tissue culture system. While in normal skin, keratinocytes did not express HLA-DR, DQ, or ICAM-1, when organ cultures were supplemented with IFN-gamma, rapid induction of keratinocyte ICAM-1 expression occurred after 24 hours; HLA-DR but not DQ expression occurred after 48 hours. TNF also induced keratinocyte ICAM-1 expression (although to a lesser degree than IFN-gamma) but did not induce either keratinocyte HLA-DR or DQ expression. There was good correlation of keratinocyte expression of ICAM-1 and HLA-DR by IFN-gamma and TNF when the epidermis of the organ culture system was compared with the isolated keratinocytes grown in tissue culture. The presence of intraepidermal lymphocytes correlated extremely well with keratinocyte ICAM-1 expression but not with keratinocyte HLA-DR expression in psoriasis, atopic dermatitis, lichen planus, and mycosis fungoides. The intensity of endothelial cell expression of ICAM-1 correlated with the degree of dermal inflammation. We conclude that IFN-gamma, once produced by activated T lymphocytes in the dermis, may be of importance in lymphocyte trafficking in the epidermis by the induction of keratinocyte ICAM-1 expression. The use of the short-term organ culture system, in which there is inducible ICAM-1 expression, provides an experimental bridge between purely in vitro and in vivo investigations to further our understanding of the molecular basis for lymphocyte apposition to keratinocytes in the skin.

Gamma interferon induces different keratinocyte cellular patterns of expression of HLA-DR and DQ and intercellular adhesion molecule-I (ICAM-I) antigens

With indirect immunofluorescence techniques we demonstrated that recombinant gamma-interferon induced the expression of the class II antigens HLA-DR and HLA-DQ as well as intercellular adhesion molecule-I (ICAM-I) on normal, cultured human keratinocytes grown in low-calcium, serum-free medium. Each antigen displayed a distinctive cellular staining pattern. HLA-DR was strongly localized to perinuclear zones with intense cell surface expression; HLA-DQ displayed a perinuclear accentuation, but with minimal cell surface staining, and ICAM-I was strongly expressed in a diffuse cytoplasmic pattern with intense cell surface expression. Keratinocytes grown in medium supplemented with 10% fetal calf serum underwent differentiation, with a diminished expression of all three antigens as compared to those grown in low-calcium, serum-free medium. These results confirm that gamma interferon can differentially regulate HLA-DR and HLA-DQ expression; that there are probably different biochemical metabolic pathways by which these three molecules are expressed on keratinocytes, and that the expression is also a function of the degree of keratinocyte differentiation. The strong cell surface expression of ICAM-I is suggested to be of major importance as the recognition molecule, by which T cells bind to gamma interferon exposed keratinocytes, and suggests an integral role for this molecule in epidermal lymphocyte trafficking.

T-cell response to purified protein derivative after removal of Langerhans' cells from epidermal cell suspensions containing keratinocytes expressing class II transplantation antigens

In a previous study we observed that human epidermal cell (EC) suspensions containing HLA-DR-expressing keratinocytes showed an amplified T-cell response to purified protein derivative (PPD). To evaluate further the possible immunological importance of class II transplantation antigens on keratinocytes we have compared the T-cell response to PPD in the presence of the following stimulator cells: EC suspensions from normal skin, or EC from tuberculin-reactive skin with or without removal of Langerhans' cells. The proliferation of purified T lymphocytes from peripheral blood in response to PPD in the presence of various concentrations of autologous EC was measured by [3H]thymidine incorporation on day 6. In 3 experiments out of 4 the EC from tuberculin-reactive skin, containing 28-76% HLA-DR-expressing cells as judged by immunocytochemistry (which also revealed fairly numerous HLA-DQ/-DP-expressing keratinocytes and a slight increase in CD36- and CD4- but not CD1-expressing cells), induced a more pronounced T-cell response to PPD than did normal EC. This was not the case in the fourth experiment, in which a small number of HLA-DR-(15%) and few if any HLA-DQ-/-DP-expressing keratinocytes were found. Immunomagnetic removal of CD1-reactive Langerhans' cells from the tuberculin-reactive EC suspensions resulted in a reduction of the T-cell response to PPD, in most cases down to background level (T cells alone + PPD). This study does not support the hypothesis that HLA-DR-expressing keratinocytes can in themselves act as antigen-presenting cells.

Immunologic mechanisms in psoriasis

This review presents evidence for the immunopathogenesis of psoriasis. T lymphocytes with human lymphocyte antigen (HLA)-DR molecules and receptors for interleukin 2 were found in the dermis of psoriatic plaques, suggesting the presence of activated T cells in these lesions. Keratinocytes in active plaques demonstrated HLA-DR molecules on their surfaces. These immunologic abnormalities were reversible with medical therapy. Keratinocyte HLA-DR expression was associated with an increased incidence of psoriatic arthritis. We propose that HLA-DR + keratinocytes and Langerhans cells in plaques could activate dermal T cells directly in an autologous mixed leucocyte/epithelial cell reaction. Alternatively, they could present an unknown autologous or exogenous antigen to T lymphocytes. T cell activation would then lead to the release of mediators of inflammation, and possibly of epidermal growth factors. This hypothesis also provides an explanation for the chronicity of psoriasis. Most of the therapies used to treat psoriasis suppress cellular immune function and inflammation. These include ultraviolet irradiation, cyclosporine, corticosteroids, methotrexate, anthralin, and retinoids.

Amplification of T-cell response to PPD by epidermal cell suspensions containing HLA-DR-expressing keratinocytes

The biological importance of the presence of class II transplantation antigens on highly differentiated epithelial cells such as keratinocytes in certain conditions, is still unknown. We have therefore investigated the antigen-presenting capacity of separated human epidermal cells obtained from tuberculin-reactive skin 6 days after intradermal injection of purified protein derivative (PPD). Earlier studies have shown a high percentage of HLA-DR-expressing keratinocytes at this time. Peripheral adherent blood cells were used as control stimulator cells and highly purified peripheral blood T lymphocytes as responder cells. The T-cell proliferation in response to PPD in the presence of autologous epidermal cells from normal and tuberculin-reactive skin was measured by [3H]thymidine incorporation on day 6. The latter cell population, 76-86% of which consisted of HLA-DR-expressing cells as judged by immunocytochemistry, induced a greater T-cell response to PPD than do normal epidermal cells. This discrepancy in the T-cell proliferation could not be explained by a difference in the numbers of anti-Leu 6 or anti-HLA-DQ-reactive Langerhans cells. The present data indicate that epidermal cell suspensions containing HLA-DR-expressing keratinocytes induce a greater T-cell response to PPD than do normal epidermal cells.

Recombinant gamma interferon induces HLA-DR expression on squamous cell carcinoma, trichilemmoma, adenocarcinoma cell lines, and cultured human keratinocytes

We investigated the effects of recombinant human gamma interferon on the induction of HLA-DR expression by two human squamous cell carcinoma, three trichilemmoma, one eccrine carcinoma, two adenocarcinoma cell lines, and cultured human keratinocytes in vitro. None of eight epithelial cell lines or keratinocytes expressed HLA-DR without gamma interferon treatment. In contrast, pure gamma interferon (500 IU/ml, 72-h treatment) induced HLA-DR expression on 1/2 squamous cell carcinoma, 3/3 trichilemmoma, 2/2 adenocarcinoma cell lines, and 4/4 keratinocyte cell lines, as determined using a fluorescence-activated cell sorter. A maxillary squamous cell carcinoma line and an eccrine carcinoma cell line failed to express HLA-DR with gamma interferon treatment; however, the growth of cells was inhibited by gamma interferon treatment. By indirect immunoperoxidase techniques, tumor cells such as Bowen's disease and squamous cell carcinoma were found to express HLA-DR. Since HLA-DR expression has been shown to be important for various immune responses, these findings suggest that gamma interferon plays important roles in various immune-related skin diseases.

HLA-DR antigen expression on keratinocytes in highly inflamed parts of psoriatic lesions

We have investigated the immunoperoxidase staining pattern in the epidermis and dermal infiltrates of highly inflamed portions of psoriatic lesions, selecting for biopsy early pinpoint lesions or margins of active plaque lesions. We found positive intercellular staining for HLA-DR antigens in localized areas of the epidermis in about half of the patients tested. In contrast, OKT6 antigen was found only on the dendritic cells in the epidermis and dermis in all cases. These findings support the hypothesis that an active cellular immune reaction involving the epidermis, possibly associated with the expression of HLA-DR antigens on keratinocytes, occurs in the highly inflamed areas of psoriatic lesions, particularly in early pinpoint lesions or at the edges of spreading plaque lesions.

Keratinocyte expression of MHC class II antigens in allergic sensitization and challenge reactions and in irritant contact dermatitis

Keratinocytes expressed major histocompatibility complex class II antigens during the development of irritant contact dermatitis, and during the induction of contact hypersensitivity, as well as in established allergic contact dermatitis. A battery of anti-class II monoclonal antibodies, some of which are specific for class II subregion products (DP, DQ, DR), was used in an immunohistochemical study of the sequential changes in the allergic challenge reactions to dinitrochlorobenzene (DNCB) and nickel, the irritant response to anthralin, and the induction of sensitization to DNCB. The induction of keratinocyte class II expression paralleled the influx of Leu-3a+ T cells into the skin and had occurred by 24 or 48 h in each type of reaction. Differential expression of class II subregion products on keratinocytes was noted: DR was the most frequently expressed molecule, followed by DP and DQ, although in the irritant response, DP expression was not observed. The importance of these observations can be decided only by functional studies.

Defined in situ enumeration of T6 and HLA-DR expressing epidermal Langerhans cells: morphologic and methodologic aspects

An essential prerequisite for the in situ enumeration of epidermal Langerhans cells (LCs) is the unequivocal identification of the desired cell type. We have examined over 250 cryostat sections of normal human skin to analyze morphologic and methodologic problems underlying the quantification of epidermal LCs, defined by anti-T6 (OKT6) and anti-HLA-DR (OKIal) immunoperoxidase staining. Our findings show that OKT6 reactivity of dendritic processes in cross-sectioned epidermis yields microscopic images which are not easy to analyze objectively. The morphology that we find leads us to categorize dendritic cells into 3 arbitrary types of T6+ LC profiles. In addition we describe criteria for the assessment of OKT6 staining patterns relating to the dendritic state of epidermal LCs. Preliminary quantitative data on this issue are discussed in relation to: epidermal thickness; the thickness of skin tissue sections; and the discrepancy between the number of T6+ and HLA-DR+ LCs. We hope that the principles outlined in this report may serve to overcome potential methodologic problems with quantitation of T6+ epidermal LCs in skin sections.

Expression of HLA-DR molecules by keratinocytes, and presence of Langerhans cells in the dermal infiltrate of active psoriatic plaques

Immunoperoxidase staining of skin sections and immunofluorescence analysis of keratinocyte suspensions obtained from suction blisters of psoriatic plaques were performed using an mAb, Josh 524.4.1, and Fab'2 fragments of a rabbit antiserum, both of which are directed against nonpolymorphic determinants of HLA-DR molecules. HLA-DR+ keratinocytes were present in plaques, but not normal-appearing skin, from a significant portion of patients with active psoriasis. Double-labelling immunofluorescence experiments with either the monoclonal or polyclonal anti-HLA-DR antibody, in conjunction with the mAb OKT6, which identifies DR+ Langerhans cells, demonstrated that HLA-DR molecules were present on OKT6- keratinocytes. The dermal infiltrate of psoriatic plaques contained T cells expressing the activation antigens, IL-2 receptor (Tac) and HLA-DR, as well as macrophages and OKT6+ cells. There was little difference in the characteristics of the dermal infiltrate between the lesions with or without HLA-DR+ keratinocytes. OKT6+ presumptive Langerhans cells were also found in the dermal infiltrates of patients with lichen planus, contact dermatitis, spongiotic dermatitis, erythema multiforme, basal and squamous cell carcinoma. Studies of keratinocyte suspensions showed that 7-84% of keratinocytes were HLA-DR+. Flow cytometry experiments showed that keratinocytes at all stages of differentiation were HLA-DR+. However, the stem cell-enriched population contained the highest proportion of HLA-DR+ cells. HLA-DR expression by keratinocytes correlated with disease activity. The expression was reversible with successful medical therapy. HLA-DR+ keratinocytes may activate T cells directly or may present an as yet unknown antigen to T cells. These studies provide further support for the hypothesis that immunological mechanisms play an important role in the pathogenesis of psoriasis.

Immunohistologic identification of antigen-presenting cells in cutaneous sarcoidosis

Considerable evidence exists to show that activated T lymphocytes preferentially accumulate at sites of disease activity in sarcoidosis. Langerhans cells, which can be recognized by reactivity with an antibody to the T6 antigen are thought to play a primary role in T-lymphocyte activation by the skin, a tissue frequently involved in sarcoidosis. This immunohistologic study examined the distribution of OKT6-positive cells and surface expression of HLA-DR antigen in cutaneous sarcoid lesions. Skin specimens stained with an anti-HLA-DR antibody demonstrated diffuse staining of the granulomas. In addition, keratinocytes, which do not normally express HLA-DR antigens, were found to stain with monoclonal antibody to HLA-DR in an intercellular pattern. Examination of specimens for OKT6-reactive Langerhans cells revealed significantly greater concentrations in the epidermis overlying sarcoidal granulomas (33 +/- 7 cells/mm) than in the epidermis of age-, sex-, and race-matched controls (11 +/- 3 cells/mm, p less than 0.001). Of greater importance was the demonstration that significant numbers of OKT6-positive cells were present within the dermal sarcoid granulomas (19-208/mm2) in a distribution that paralleled that of Leu-3a-positive T lymphocytes. These data suggest that the epidermis may participate in activation of lymphocytes in cutaneous sarcoidosis, and implicate OKT6-positive cells in granuloma formation.

HLA-DR expression on keratinocytes is a common feature of diseased skin

Biopsy specimens from 185 patients with 52 different skin disorders were investigated by indirect immunofluorescence staining for the presence of HLA-DR bearing keratinocytes and their association with an underlying inflammatory infiltrate and in particular with activated (HLA-DR-positive, Leu-4-positive) T lymphocytes. HLA-DR expression on keratinocytes was demonstrated in 38 dermatoses, including lymphocytic vasculitis, lupus erythematosus, morphea, vitiligo, lichen planus, cutaneous T-cell lymphoma, various infectious dermatoses, allergic contact dermatitis, granulomatous dermatoses, Sweet's syndrome, lichen sclerosus and erythema nodosum. In 27 of these this had not previously been reported. Occurrence of HLA-DR on keratinocytes was invariably linked to the presence of a lymphocytic infiltrate containing numerous activated T-cells (Leu-4 +, HLA-DR +) whereas such infiltrates were not accompanied by HLA-DR expression on keratinocytes in all the dermatoses investigated, as in pseudolymphoma and erythema anulare centrifugum. However, HLA-DR positive keratinocytes were consistently absent in skin disorders lacking any significant lymphocytic infiltration (e.g. leukocytoclastic vasculitis, bullous autoimmune dermatoses, genodermatoses and mastocytosis). Although it has been suggested that HLA-DR-positive keratinocytes are involved in various immune responses of the skin, their exact functional significance is, as yet, unknown.

Expression of HLA-DQ antigens on keratinocytes in Borrelia spirochete-induced skin lesions

Skin biopsies were investigated with two different immunohistochemical techniques, thus revealing HLA-DQ antigens on HLA-DR-expressing keratinocytes in the late skin manifestations of a Borrelia spirochete infection. In the early skin lesions only HLA-DR antigens were present on the keratinocytes. The invariant gamma chain of class II transplantation antigens was observed on keratinocytes in 1:5 of the late cases. Upon penicillin treatment detectable HLA-DR and HLA-DQ antigens disappeared completely from the keratinocytes. Furthermore, the mononuclear cell infiltrates dominated by anti-Leu 1 and anti-Leu 3a-reactive cells and containing many cells with markers for activation (HLA-DR, HLA-DQ, transferrin, and interleukin 2 receptors) diminished markedly. The possibility that the expression of different class II transplantation antigens on keratinocytes might reflect separate functional demands of these cells or an altered immunological reactivity in the host, is discussed. The precise functional role of the temporary expression of the class II antigens on non-lymphoid cells, however, remains an enigma.

Reactivity pattern of anti-CD1 and anti-HLA class II monoclonal antibodies with human eccrine sweat glands

The known cross-reactivity of monoclonal antibodies prepared against CD1 and HLA-DR antigens with skin components prompted us to study the reactivity pattern of human eccrine sweat glands with a panel of monoclonal antibodies directed against CD1 antigens (OKT6, BL6, D-47) and against HLA-class II antigens (anti-DR, BL2, LEU-10, IV-D12, MAJA-7). The labelling pattern of eccrine glands with the panel of monoclonal antibodies used in this study permits to establish three different antigenic compartments on eccrine glands: 1) acrosyringium and distal part of dermal duct anti-DR+, BL2+, LEU-10+, IV-D12+; 2) proximal part of dermal duct MAJA-7+; 3) secretory part D-47+. The immunological markers used in this work provide a useful tool for investigation of eccrine gland differentiation and human eccrine glandular pathology.

Expression of HLA-DR by anagen hair follicles in alopecia areata

The expression of HLA-DR within hair follicles in alopecia areata was studied using an immunoperoxidase method. Scalp biopsies were taken from 12 patients with alopecia areata and from 6 normal control subjects. Frozen sections were stained with a panel of 4 anti-HLA-DR monoclonal antibodies, Leu 2, Leu 3, Leu 4, and T6 antibodies. The expression of DR in normal hair follicles and in most anagen follicles from nonlesional alopecia skin was confined to dendritic cells which were sparse below the level of the arrector pilorum insertion. Of the 37 anagen follicles examined in lesional skin, 25 displayed staining for DR on epithelial cells in the precortical matrix and presumptive cortex. Six follicles showed DR staining in other epithelial compartments, the lower bulb matrix, inner root sheath, and outer root sheath. Infiltration of the hair bulb matrix by T cells was seen in the majority of follicles where epithelial cells were DR+. The aberrant expression of DR antigens by hair follicle epithelium provides direct evidence that immune mechanisms are operating in the pathogenesis of alopecia areata. In a previous study of alopecia areata we found evidence of cell injury confined to the precortical matrix and presumptive cortex in lesional anagen follicles. The relative restriction of epithelial DR expression to the same site suggests that this region of the follicle is of fundamental importance in the disease process.

Flow cytometry sorting of unlabelled epidermal Langerhans cells using forward and orthogonal light scatter properties

A variety of techniques based on the presence of specific markers has been proposed to enrich Langerhans cells from epidermal cell suspensions. Computer analysis of multiparameter flow cytometry records involving forward angle and orthogonal scattered light and immunofluorescence of epidermal cells allowed us to determine the scattering properties of Langerhans cells. Unlabelled cells sorted according to these properties were shown to be Langerhans cells by electron microscopy and/or subsequent labelling by anti-HLA-DR monoclonal antibody. The relevance of this method is discussed to sorting viable Langerhans cells which may be used in functional studies and for establishing long-term culture.

Enrichment of murine and human Langerhans cells with solid phase immunoabsorption using pan-leukocyte monoclonal antibodies

Using a solid phase immunoabsorption (panning) technique, we have employed pan-leukocyte monoclonal antibodies to enrich and deplete murine and human Langerhans cells from cell suspensions of normal skin. Langerhans cell-enriched fractions contained 80-99% mononuclear cells, almost all of which had the ultrastructural features of Langerhans cells. These results are comparable to those achieved by panning for human Langerhans cells with anti-Leu-6(T6) antibody. Similarly, less than 1% of these cells were detectable in Langerhans cell-depleted fractions and such fractions were incapable of stimulating allogeneic lymphocytes in the skin cell-lymphocyte reaction. We conclude that panning with pan-leukocyte antibodies is an effective means of enriching or depleting Langerhans cells from heterogeneous skin cell suspensions and can yield results similar to those achieved with more Langerhans cell-specific reagents such as anti-Leu-6(T6). These findings are of particular significance to the enrichment and depletion of murine Langerhans cells since they express no known correlate of the human Leu-6(T6) antigen.

Recombinant gamma interferon differentially regulates class II antigen expression and biosynthesis on cultured normal human keratinocytes

Recombinant gamma interferon induces class II antigen (HLA-DR) biosynthesis and expression on normal cultured human keratinocytes. HLA-DR expression was not induced on keratinocytes by recombinant alpha or beta interferons in a similar dose range nor by Con A or PHA. HLA-DR (L243) expression, as determined by FACS analysis, was detected as early as 1-2 days after addition of r-IFN-gamma to the cultures and was maximal after 4-8 days. Keratinocytes were analyzed for expression of another class II antigen, HLA-DC (Leu-10). Little or no expression of Leu-10 (DC) was detectable on these cells although Fc receptors for the IgG1 isotype were increased. These data indicate a unique role for gamma interferon in the differential regulation of keratinocyte class II antigen biosynthesis and expression. Induction of HLA-DR on keratinocytes may be functionally important in expanding the number of antigen presenting cells in the skin for the induction of an immune response and/or targeting these keratinocytes for cytolysis.

Recombinant gamma interferon induces HLA-DR expression on cultured human keratinocytes

In normal human epidermis, expression of HLA-DR antigen is restricted to Langerhans cells (LC) and acrosyringial epithelium. However, in diseases such as lichen planus and graft-vs.-host, HLA-DR antigen appears to be expressed by keratinocytes, although the exact source of the HLA-DR is unclear. Two possibilities are that (1) the HLA-DR is shed by neighboring immunocompetent cells, or (2) that the keratinocytes are synthesizing the antigen themselves. Recently, gamma interferon has been shown to induce HLA-DR biosynthesis and expression on human malignant melanoma cells lines and on normal vascular endothelium. We report here that pure recombinant human gamma interferon (100 units/ml) induces HLA-DR expression on 60-70% of cultured human adult keratinocytes depleted of LC within 2-4 days of culture as determined by fluorescence-activated cell sorter (FACS) analysis using monoclonal antibodies. No residual LC or lymphocytes could be detected in these cultures. This is the first demonstration of HLA-DR expression by cultured human keratinocytes. This expression may be of functional significance in antigen presentation and cell-mediated cytotoxicity involving the epidermis.

Epidermal Langerhans cells contain intermediate-sized filaments of the vimentin type: an immunocytologic study

In epidermal cell suspensions, prepared from healthy human and murine skin, Langerhans cells (LC) were identified by indirect immunofluorescence microscopy using monoclonal antibodies directed against human T6 and Ia markers, and against a murine Iak determinant, respectively. The cells were double-labeled on cytospin slides with antibodies against a cytoskeletal protein, either vimentin or keratin. In this way it was shown that epidermal LC contain intermediate-sized filaments of the vimentin type.