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Intraepidermal dendritic cells react with the monoclonal antibody, anti-T6, which also reacts with a majority of cortical thymocytes but not with mature T lymphocytes. Application of a four-step peroxidase antiperoxidase technique and immunoelectron microscopy to normal human epidermis demonstrates that T6 antigen is present on the cell surface of Langerhans cells but not on keratinocytes or melanocytes. These data suggest that T6 antigen is an important marker for Langerhans cells.

We have demonstrated the presence of the glycoprotein T200 on the surface of human epidermal Langerhans and indeterminate cells by immunoelectron microscopy with the use of a monoclonal antibody. No other epidermal cells were positive. The presence of T200 on Langerhans cells confirms their hematopoietic origin because T200 is limited to hematopoietic cells and neoplasms. Although the function of T200 is not known, antibodies directed against T200 have been previously shown to inhibit accessory cell and natural killer cell activities. While the existence of a possible relationship between Langerhans cells and natural killer cells is unclear, Langerhans cells are important in cutaneous accessory cell functions; therefore. T200 may be important in understanding the biology of Langerhans cells and their relationship to other cells in the immune response.

To identify the infiltrating mononuclear cells in conjunctival lesions, we stained frozen tissue sections of conjunctiva with a series of monoclonal antibodies against T cells and T-cell subsets with an immunoperoxidase method. In vernal conjunctivitis and ocular pemphigoid, most lymphocytes reacted with the anti-T4 antibodies that define helper/inducer T cells (T4+); a minority reacted with the anti-T8 antibody that defines suppressor/cytotoxic T cells (T8+). However, T8+ cells predominated in a conjunctival specimen from a patient with chronic graft-vs-host disease. A few T8+ cells and rare T4+ cells were also found in normal conjunctiva. In some diseased conjunctivas, there was an increase in cells stained with anti-T6 antibody, which stains Langerhans cells in normal conjunctiva and skin. T lymphocyte subsets and Langerhans cells probably play an important role in the pathogenesis of inflammatory conjunctival lesions.

A peroxidase-antiperoxidase study using monoclonal antibodies directed against T and B lymphocytes and Langerhans cells/indeterminate cells (LC/IC) was undertaken in order to understand more clearly the changes observed in erythema multiforme. At the various stages of development, from normal skin to target lesions, the quantity of inflammatory cells differed, but in each case the number of T8+ (cytotoxic/suppressor) cells was greater than the number of T4+ (helper/inducer) cells in the epidermis, whereas the latter exceeded the former in the dermis. Concomitant with the initial epidermis changes, there was an increase in the number of T6+ (LC/IC) cells in the upper and lower epidermis. With slight to moderate basal unit destruction, the number of LC/IC in the upper epidermis exceeded those in the lower epidermis. With severe basal unit destruction, there was a loss of LC/IC in the lower epidermis as detected by T6 reactivity. In fully formed blisters, the LC/IC in the upper half of the epidermis were decreased in parallel with the degree of epidermal necrosis. The character of the lymphocytic inflammatory infiltrate and redistribution in LC/IC are similar to those findings described in allergic contact dermatitis. The clinical, histologic, and immunopathologic changes in erythema multiforme appear to be due in part to cellular immune mechanisms with the lymphocyte as the predominant effector cell, and our data suggest a possible role for LC/IC in this disorder.

We observed the apparent migration of Langerhans cells across the basal lamina of normal human skin by immunoelectron microscopy using monoclonal anti-T6 antibody. This technique made it possible to visualize cytoplasmic processes of Langerhans cells not normally detectable by routine transmission electron microscopy, and therefore facilitated the documentation of the migratory process. Although events early in the migratory sequence were not observed, perhaps as the result of the evanescent nature of this phase, the association of Langerhans cells with focal disruptions in the epidermal basal lamina was documented. The basal lamina adjacent to these Langerhans cells was electron lucent, granular in character, and thinned, or intact, suggesting sequential reassembly after disruption. This study provides ultrastructural documentation supporting the hypothesis of ongoing migration of Langerhans cells across epidermal membranes, and suggests that this process is mediated by the disruption and reconstitution of the epidermal basal lamina.

Previous studies in our laboratory using immunoelectron microscopy have shown that anti-T6 monoclonal antibody reacts with all epidermal Langerhans cells in normal skin. Comparison of the number of T6-positive (+) epidermal cells with Ia (HLA-DR) (+) cells, as defined by the monoclonal antibodies, anti-I1 and anti-I2, disclosed that these latter markers significantly underestimated Langerhans cell and indeterminate cell numbers (p less than 0.01 and p less than 0.001, respectively) when employed in a sensitive 4-step immunoperoxidase procedure. Thus, it appears that all epidermal Langerhans cells and indeterminate cells are not Ia-positive as defined in this system and that Ia(+)/T6(+) and Ia(-)/T6(+) subsets exist. These subsets may be analogous to the Ia(+) and IA(-) subsets of macrophages, in which the former are responsible for antigen interaction with T cells.

Skin biopsies from four patients with lichen planus were studied using monoclonal antibodies directed against T lymphocytes. Anti-TI and anti-T3 antibodies, which react with all peripheral T cells, stained most cells in the dermal infiltrates. The majority of infiltrating cells also stained with anti-T4 and anti-T4b antibodies, which react with helper/inducer cells, whereas a minority of cells stained with anti-T8 antibody, which reacts with cytotoxic/suppressor cells. Surface IgM was not identified on any infiltrating cells, providing evidence against B cell participation. Intraepidermal and dermal cells with long cytoplasmic extensions stained with any anti-T6 antibody in all cases, defining them as Langerhans cells or their precursors. T6-positive cells were seen in greater number than in normal control epidermis and dermis. The results indicate that well-developed lesions of lichen planus are characterized by an influx of helper/inducer T lymphocytes and increased numbers of Langerhans cells. These observations support the contention that cellular immunity is important in the pathogenesis of this disorder.

To determine a possible role of Langerhans cells in viral infection of skin, we studied the distribution of Langerhans and indeterminate cells in the lesional skin of mollusca contagiosa, verrucae vulgaris, plantar warts, and condylomata acuminata. A total absence of Langerhans and indeterminate cells was observed in molluscum contagiosum, but their number appeared to be normal or increased in the perilesional normal skin. Few Langerhans and indeterminate cells were seen in the suprabasal location in verrucae vulgaris and plantar warts, and normal numbers were noted in the perilesional skin. In contrast, a larger number of Langerhans and indeterminate cells reaching up to stratum granulosum were found in the condylomata acuminata. It is possible that alteration of keratinocytes by viral infection may effect the migration of Langerhans cells to the epidermis. The lack of Langerhans cells may lead to a paucity of inflammatory response (in particular, T cell-mediated response) to the cells infected with the virus.

The distribution of the major histocompatibility antigens HLA-A,B,C, (HLA) on dendritic cells of normal human skin was studied by immunoelectron microscopy and a 4-step immunoperoxidase technique utilizing monoclonal antibodies. Light microscopy revealed peripheral staining for HLA of epidermal and pilar infundibular keratinocytes. In the epidermis, the staining was present from the basal layer to the upper stratum spinosum. In the follicles below the level of the infundibulum, HLA was detected only on rare intraepithelial dendritic cells. These dendritic cells could not be identified in the epidermis due to the HLA staining of the surrounding keratinocytes. Similar cells stained diffusely with anti-T6 antibody; the keratinocytes did not. Immunoelectron microscopy demonstrated: (1) the presence of HLA staining of keratinocyte membranes from the stratum basalis to the level of the upper stratum spinosum and in the pilar infundibulum, (2) the possible absence of HLA on melanocytes, (3) the presence of focal HLA staining of the membranes of epidermal and follicular dendritic cells that contained Birbeck granules and were, therefore, Langerhans cells, (4) dendritic mononuclear cells within the follicular epithelium, which although devoid of Birbeck granules, exhibited similar reactivity with anti-HLA antibody. These findings suggest that HLA antigens are present on the membranes of Langerhans cells, but are not demonstrable on melanocytes in normal human skin.

Cutaneous lesions in three cases of histiocytosis-X were studied by light microscopy, electron microscopy, and immunoperoxidase technics. In each case, Birbeck granule-containing histiocytosis-X cells infiltrated the epidermis and were apposed to lymphocytes. The histiocytosis-X cells and normal Langerhans cells stained with anti-T6 and anti-I1 (Ia-like) antibodies but were negative with anti-T3, anti-T8, anti-M1, and anti-lysozyme antibodies. In addition, the histiocytosis-X cells also stained with anti-T4 antibodies, which react with T-cells associated with helper/inducer phenotype. This study supports the hypothesis that histiocytosis-X cells are abnormal Langerhans cells. The presence of T4/T6-positive cells in cutaneous disease may be a marker for abnormal Langerhans cells.

Biopsy specimens of papules taken from eight patients with polymorphic Light eruption were examined by immunoperoxidase techniques employing monoclonal antibodies. In each case, most infiltrating mononuclear cells were T cells. The majority of T cells were TB-positive (cytotoxic/suppressor) in four cases and T4-positive (helper/inducer) in two. In two cases, approximately equal numbers of both T cell subsets were present. In only three cases were rare B cells identified by their reactivity with anti-IgM antibody. M1-positive mononuclear cells (macrophages) represented less than 5% of cells infiltrating the dennis. In five subjects, anti-T6 antibody stained increased numbers of dermal mononuclear cells considered to be Langerhans/indeterminate cells. The pathogenesis of papular polymorphic tight eruption may involve injury to upper dermal venules mediated by T cells and Langerhans/ indeterminate cells. [ABSTRACT FROM AUTHOR]

Skin biopsies from four patients with lichen planus were studied using monoclonal antibodies directed against T lymphocytes. Anti-T1 and anti-T3 antibodies, which react with all peripheral T cells, stained most cells in the dermal infiltrates. The majority of infiltrating cells also stained with anti-T4 and anti-T4b antibodies, which react with helper/inducer cells, whereas a minority of cells stained with anti-T8 antibody, which reacts with cytotoxic/suppressor cells. Surface IgM was not identified on any infiltrating cells, providing evidence against B cell participation. Intraepidermal and dermal cells with long cytoplasmic extensions stained with anti-T6 antibody in all cases, defining them as Langerhans cells or their precursors. T6-positive cells were seen in greater number than in normal control epidermis and dermis. The results indicate that well-developed lesions of lichen planus are characterized by an influx of helper/inducer T lymphocytes and increased numbers of Langerhans cells. These observations support the contention that cellular immunity is important in the pathogenesis of this disorder. [ABSTRACT FROM AUTHOR]

We have observed that monoclonal antibodies directed against human Ia-like antigens react with a subset of epidermal keratinocytes as well as Langerhans cells in normal human skin. Membrane reactivity for HLA-DR antigen in flattened ductal keratinocytes and in adjacent cuticular cells forming the acrosyringial lumen was observed using immunoelectron microscopy. It should be recognized that Ia-positive acrosyringial keratinocytes represent a potential source of contamination in methods designed to study and isolate Langerhans cells using antibodies directed against HLA-DR antigens. Teleologic considerations of HLA-DR antigen expression in the acrosyringium are discussed. [ABSTRACT FROM AUTHOR]