Mixed skin cell-lymphocyte culture reaction (MSLR) as a model for the study of lympho-epidermal interactions

T-cell costimulatory capacity of oral and skin epithelial cells in vitro: presence of suppressive activity in supernatants from skin epithelial cell cultures

Oral Langerhans cells (LC) have better T-cell costimulatory capacity than skin LC. In this study factors affecting this capacity have been assessed in a mixed epithelial cell lymphocyte reaction (MELR) assay. Flow cytometry analysis of freshly recovered cells revealed major histocompatibility complex (MHC) class II molecule expression on 7.5% of the oral epithelial cells and 9.7% of the skin epithelial cells. Monoclonal anti class II antibodies significantly reduced the T-cell proliferation in the MELR. Pretreatment of skin epithelial cells with interleukin-1beta, tumour necrosis factor-alpha or interferon (IFN)-gamma did not affect the MELR proliferation, but incubation with IFNgamma significantly suppressed the T-cell response. Transfer of supernatants from cultures of skin epithelial cells and allogeneic T cells to cultures of oral epithelial cells and T cells resulted in a reduced T-cell proliferation while supernatants from oral epithelial cells and T cells did not reduce proliferation. The higher proliferation in cultures of T cells and oral epithelial cells than in cultures containing skin epithelial cells may be due to the presence of a suppressive factor in the skin epithelial cell suspensions.

Cytokine regulation of major histocompatibility complex antigen expression by human oral and skin keratinocytes

The expression, and cytokine modulation, of major histocompatibility complex (MHC) class I and class II molecules on oral and skin keratinocytes were compared in cell culture. Both cell types expressed class I, but not class II, constitutively. However, stimulation with interferon-gamma, but not interleukin-1 alpha, and -1 beta, tumour necrosis factor-alpha or lymphotoxin, induced increased expression of class I and de-novo expression of HLA-DR on both cell types. Oral keratinocytes differed from skin keratinocytes in that they exhibited greater sensitivity to interferon-gamma stimulation and higher stimulated expression of both class I and HLA-DR. In addition, interferon-gamma stimulated oral, but not skin, keratinocytes to express HLA-DP and -DQ. These observations suggest that, like skin keratinocytes, under certain conditions, oral keratinocytes may be able to act as antigen-presenting cells. This may be important in the initiation and progression of some immune-mediated mucocutaneous diseases. Moreover, differences in MHC expression may help to explain differences in the presentation of these diseases on the skin and oral mucosa.

Effect of IFN-gamma on the expression of MHC class I and class II antigens in a human malignant oral epithelial cell line

This study examined the expression of major histocompatibility complex (MHC) antigens in the KB human carcinoma cell line. MHC class I antigens (HLA-ABC and beta 2microglobulin) were constitutively expressed but not significantly enhanced by interferon-gamma (IFN-gamma). By contrast, MHC class II antigens were absent or expressed minimally on unstimulated KB cells, but DR and DP were significantly stimulated in a non-coordinated pattern (HLA-DR greater than -DP greater than -DQ) by IFN-gamma.

Detection and quantitation of HLA class II molecules on keratinocytes by quantitative immunofluorescence

The paper describes measurements of HLA-DR antigen expression on normal human keratinocytes in culture using anti-HLA-DR antibodies and fluorescent Protein A or fluorescent second antibody methods and a low-light level video camera and image analysis program to quantitate the fluorescence output. The measurements are ultimately quantitated in terms of molecules of Ia antigen reacting material per cell. The method has a sensitivity at a S/N ratio of 10:1 of 180 molecules/micron2. The results show that normal keratinocytes do indeed express class II antigens on their surfaces at levels well above background. We confirm that treatment of the cells with gamma-interferon produces enhanced expression of DR antigens within 4 days. The method of quantitation is applicable to fluorescence and other low light level images.

Anomalous expression of HLA class II molecules on keratinocytes and fibroblasts in hypertrophic scars consequent to thermal injury

Immunoperoxidase staining of skin sections obtained from 11 hypertrophic scars, six normotrophic scars and three samples of normal skin were performed using anti-HLA monoclonal antibodies (HLA-DR, -DQ, class I), anti-interleukin-2 receptor (IL-2R) and anti-CD1. Sections from all hypertrophic scars showed an anomalous expression of HLA-DR molecules on keratinocytes and fibroblasts. Moreover hypertrophic scars were characterized by dense infiltrates of IL-2R-positive cells and by the presence of abundant Langerhans (CD1+) cells in the epidermis and dermis. These results support the hypothesis that immunologic mechanisms play an important role in hypertrophic scarring and point to an involvement of cell-mediated immune phenomena.

Human gingival Langerhans cells stimulate allogeneic lymphocytes: requirement for MHC class II antigens

Langerhans cells (LC) are antigen-presenting cells which express high levels of Class II MHC antigens on their plasma membranes. While the expression of these antigens on gingival LC has been documented, their functional significance is unclear. In this study, the mixed epithelial cell-lymphocyte culture reaction (MECLR) between stimulator cells (LC) and allogenic lymphocytes was used as an in vitro model for investigating the role of the MHC Class II antigens HLA-DR, -DQ, and -DP in alloantigen presentation by gingival LC. In epithelial cell suspensions prepared from human gingiva, MHC Class II antigen expression (HLA-DR, -DP, -DQ) was confined to CD1a-positive LC. Depletion of Class II antigen-bearing LC from epithelial cells using monoclonal antibodies (L243, B7/21, and SK10) and complement inhibited the ability of epithelial cells to stimulate proliferation in the MECLR. Pre-treatment of epithelial cell suspensions with the same monoclonal antibodies suppressed proliferation in the MECLR, as did direct addition of these antibodies to co-cultures of epithelial cells and lymphocytes. These results indicate that HLA-DQ and -DP, together with DR antigens on gingival LC, are involved in LC-lymphocyte interactions. Since LC are potent antigen presenting cells, alterations in the expression of MHC Class II antigens on the surface of these cells will influence their ability to stimulate lymphocytes during the initiation of the cellular immune response to the accumulation of dental plaque.

HLA DR and DQ expression on human retinal pigment epithelial cells in vitro

In a previous immunohistopathological study, we demonstrated a deviant expression of class II antigens on the uveal pigment epithelial cells of patients with proliferative diabetic retinopathy. The mechanisms triggering this abnormal expression by epithelial cells are not well known, and we tried to induce this phenomenon on primary cultures of human retinal pigment epithelial (RPE) cells. Confluent RPE-cell monolayers were supplemented with several biological or chemical reagents [recombinant interferon gamma, phytohemagglutinin A-P (PHA-P), phorbol-myristate acetate (PMA), recombinant interleukin-2, fibroblast growth factor (FGF), Insulin], to investigate their ability to induce HLA DR and DQ expression. On days 1, 3 and 5 after stimulation, the cells were incubated with monoclonal antibodies directed against human class II antigens: all reagents used failed to induce class II antigen: all reagents used failed to induce class II antigen expression. However, on day 7, we demonstrated the presence of numerous positive HLA DR and HLA DQ cells stimulated by gamma interferon, the percentages being closely related to the dose of this lymphokine. These findings, together with those of other investigators and our previous work on uveal pigmented epithelial cells in diabetic patients, may shed light on the exact implication of RPE in many poorly documented ocular diseases.

Epithelial dendritic cells in pathological human oral tissues

Epithelial dendritic cells (EDC) were examined in human oral tissues with non-specific keratosis, lichen planus and squamous cell carcinoma. Acetone-fixed frozen sections were stained using an indirect immunoperoxidase technique and monoclonal antibodies to the human CD1 thymocyte (OKT6) and HLA-DR antigens. Significantly more T6+ and DR+ EDC were present in lichen planus tissues than normal controls, tissues with non-specific keratosis and the epithelial overlying/adjacent to squamous cell carcinomas, the latter tissues having comparable numbers of both T6+ and DR+ EDC. By contrast, significantly fewer T6+ EDC and significantly more DR+ cells were present in the invasive epithelium of squamous cell carcinomas than the overlying/adjacent epithelium of carcinomas, the non-specific keratosis group and the normal tissues. 23-60% of pathological tissues had either focal or general DR+ reactivity in keratinocytes, but there was no correlation between the density of T6+ or DR+ EDC and the keratinocyte DR status of the tissues. The results suggest that immunological enhancement occurs in lichen planus and possibly immunological impairment may characterize invasive squamous cell carcinoma.

HLA DR and DQ distribution in normal human ocular structures

HLA DR and DQ distribution was investigated in normal human ocular tissues, together with class I antigens and immunocompetent cell subsets, by immunofluorescence and immunoperoxidase procedures. In the anterior segment, our findings, consistent with those of previous reports, showed the wide distribution of class I antigens, specially in the corneal epithelium, while class II antigens were restricted to very rare cells scattered in the conjunctiva, the peripheral cornea and the stroma of the ciliary processes. Some non pigmented epithelial cells of the ciliary processes were HLA DR and DQ positive. In the posterior segment, class I antigens were abundantly represented in the choroid and the retinal layers. Few HLA DR and DQ positive cells were seen in the choroid, similar to those found in the anterior segment. Normal RPE did not react with any monoclonal antibody, but numerous cells located in the retina were strongly HLA DR and DQ positive, all around the blood vessels, and not at the sites of endothelial cells. The characterization of those cells, which could be hypothetized as pericytes needs further studies but suggests close relationships between neuroretina and the immune system. This study may provide insight in the implication of the immune system in many poorly understood ocular diseases.

A method for the rapid isolation of human epidermal Langerhans cells using immunomagnetic microspheres

Because Langerhans and indeterminate cells are the only epidermal cells that express the specific CD1a surface antigen T6, we have used immunomagnetic monodisperse polymer microspheres for positive selection of human epidermal Langerhans and indeterminate cells. Epidermal cells in suspension are successively incubated with a murine monoclonal anti-T6 antibody of the IgG1 subclass and then with magnetic beads coated with a sheep anti-mouse IgG1. Rosetted cells are obtained and then easily separated from the non-rosetted cells using a magnet. The two cell fractions are characterized by phase contrast microscopy, immunofluorescence, electron microscopy, and the skin cell-lymphocyte reaction. All the rosetted cells (1.5 to 5% of the total epidermal cells) express T6 antigen by indirect immunofluorescence and under the electron microscope possess all the ultrastructural characteristics of Langerhans cells. Moreover, the rosetted Langerhans cells remain functional: Under the electron microscope they internalize by receptor-mediated endocytosis gold labeled anti-T6 antibody, and in the skin cell-lymphocyte reaction they stimulate allogeneic lymphocytes. In contrast, the rosette depleted cell fraction is deprived of T6 positive cells and unable to stimulate allogeneic lymphocytes. The immunomagnetic depletion of epidermal cells is a simple and rapid method to isolate functional human Langerhans cells with good yield and high purity (97%). This technique should be of value in the study of the pharmacology of Langerhans cells and in the investigation of the interactions of Langerhans cells with keratinocytes or lymphocytes.

The relationship between epithelial Ia expression and the inflammatory cell infiltrate during experimental oral carcinogenesis

The development of oral epithelial expression of Ia antigens and its relationship to the presence of IL-2r+ (CD25+) cells was investigated in rats treated with the water soluble carcinogen 4-nitroquinoline-N-oxide (4NQO). Acetone fixed frozen sections of the palate and tongue were stained using an indirect immunoperoxidase technique and monoclonal antibodies to rat Ia (I-A & I-E) and IL-2 receptor. After 4 weeks 4NQO treatment all rats expressed oral epithelial Ia but thereafter (2-9 months) expression was present in only 20-40% of animals. Epithelial expression of Ia by histologically normal, dysplastic and neoplastic epithelium was always associated with the presence of an underlying inflammatory cell infiltrate containing CD25+ cells. Overall there were significantly more CD25+ cells in tissue specimens containing Ia+ epithelium compared with Ia- epithelium. Furthermore, during the first 4 weeks of carcinogen treatment, a significant positive correlation was found between the CD25+ cell density and occurrence of focal epithelial Ia expression. These results, together with analysis of the T cell, NK cell, macrophage and B cell content of the infiltrates induced by 4NQO, suggest that the CD25+ cells represent activated T cells. Thus, our results in this experimental model are consistent with the idea that epithelial expression of Ia is the result of production of IFN-gamma by locally activated T cells.

Functional analysis of Ia antigen-bearing keratinocytes: mixed skin lymphocyte culture between Ia antigen-bearing Pam 212 cells and allogeneic and syngeneic splenic T cells

Keratinocytes express Ia antigens in various skin disorders, although the biological role of these Ia antigen-bearing (Ia+) keratinocytes remains unclear. We induced Ia antigens on Pam 212 murine keratinocyte cell line by interferon-gamma(IFN-gamma) and using these cells, we performed the mixed skin lymphocyte culture with syngeneic BALB/c or allogeneic C3H/He splenic T cells. Unexpectedly, Pam 212 cells were found to stimulate both syngeneic and allogeneic T cells irrespective of IFN-gamma treatment. However, both syngeneic and allogeneic T cells cultured with IFN-gamma-treated Pam 212 cells incorporated [3H]thymidine much more actively than those cultured with IFN-gamma-untreated Pam 212 cells. This stimulation was not inhibited by monoclonal anti-I-Ad antibody. Analysis of the responding T cells demonstrated that the syngeneic T-cell stimulation by IFN-gamma-treated Pam 212 cells occurred in both purified Lyt 1-T cells and Lyt 2- T cells. Furthermore, we found that the T cells cultured with the IFN-gamma-treated cells were composed of two morphologically different types of cells. Determination of their surface phenotype showed that the small cell population consisted of 57% Thy-1+, 23% Lyt-1+, 6% Lyt-2+, and 9% asialo-GM1+ cells, while the large cells consisted of 53% Thy-1+, 15% Lyt-1+, 9% Lyt-2+, and 24% asialo-GM1+ cells. These findings suggest that IFN-gamma-treated Pam 212 cells could stimulate more than one kind of splenic T cell populations.

Stimulation of T cells by autologous mononuclear leukocytes and epidermal cells in psoriasis

Based on reports suggesting aberrant cell-mediated immunity and altered infiltration of immunocompetent cells into the skin in psoriasis, we studied the stimulation of T cells by autologous non-T mononuclear leukocytes (autologous mixed lymphocyte reaction, AMLR) and by epidermal cells isolated from lesional and clinically uninvolved skin in psoriasis (autologous mixed epidermal cell lymphocyte reaction, AMECLR). Age- and sex-matched individuals served as controls. We found that the AMLR in psoriasis (n = 11) was similar to that in healthy controls (n = 16); furthermore, cell proliferation was alike in the presence of either 5% AB-serum or autologous serum. By contrast, while the AMECLR in healthy controls (n = 9) resembled that in psoriatics employing epidermal cells from univolved skin, epidermal cells from lesional sites (n = 10) induced a significantly higher proliferation of autologous T cells in the AMECLR (P less than 0.01). We conclude that the in vitro stimulation of T cells by non-T mononuclear leukocytes is normal in psoriasis and is not regulated by autologous serum. Lesional psoriatic epidermal cells, however, are more active in stimulating autologous T cell proliferation than cells from univolved psoriatic or normal epidermis.