Thy-1 antigen-bearing dendritic cells populate murine epidermis

Two distinct cell populations, melanocytes and Langerhans cells (LC), have been recognized previously to possess dendritic configuration in normal mammalian epidermis. Employing immunofluorescence microscopy with monoclonal antibodies against Thy-1.2 antigen to identify cells in whole mounts of murine epidermis, we have identified a third dendritic cell population which differs from both LC and melanocytes. Thy-1 antigen-bearing (Thy-1+) epidermal cells are primarily dendritic, although round and angular forms may be found. They are distributed relatively evenly across skin surfaces, although densities vary greatly from site to site and from strain to strain. Densities were highest in ear epidermis from the pigmented strain B10.A (580 cells/mm2), a value approaching that of epidermal LC, and were lowest in ear epidermis from the albino strain BALB/c (5 cells/mm2). Thy-1+ epidermal cells possess neither Ia antigens nor substantial amounts of melanin, and their surface distributions are disparate from those of both LC and mature melanocytes. We propose that at least some of these cells are T lymphocytes whose malignant counterparts account for cutaneous T-cell lymphomas.     

Thymus-independent generation of Thy-1+ epidermal cells from a pool of Thy-1- bone marrow precursors

Thy-1+ dendritic epidermal cells (Thy-1+ DEC) and immature thymocytes share several phenotypic features: CD45+, Thy-1+, asialo-GM1+, CD3+, CD4-, and CD8-. In view of this similarity, it has been suggested that the epidermis may be a site of either post-thymic or extra-thymic T-cell development. In order to address this issue, we used C3H/He/Han (Thy-1.2)----AKR/Ola (Thy-1.1) radiation bone marrow chimeras. Animals were first either thymectomized or sham-thymectomized, then lethally irradiated (750R) and, finally, reconstituted with allogeneic bone marrow cells previously depleted of Thy-1-bearing cells. Six weeks after bone marrow transplantation, spleens and lymph nodes of sham-treated animals, but not of thymectomized animals, contained large numbers of CD3+ donor-type Thy-1+ cells. The epidermis of both thymectomized and sham-treated animals contained not only many recipient-type CD3+, Thy-1+ DEC, but also small numbers of CD3-, donor-type Thy-1+ cells. After 4 months, the frequency of donor cells had greatly increased, but they still lacked CD3 antigens. Most of the donor cells had a rounded shape, but some exhibited a dendritic configuration. These results demonstrate that Thy-1- bone marrow-derived precursors of Thy-1+ DEC can migrate to the epidermis without thymic influence and yet acquire Thy-1 antigens during their journey. Although donor-type Thy-1+ epidermal cells failed to mature into CD3+ dendritic epidermal cells, the experimental model used in this study may be a versatile tool for studying the influence of thymic and extrathymic epithelia on T-cell maturation.     

Fluorescence microscopic and flow cytometric analysis of bone marrow-derived cells in human epidermis: a search for the human analogue of the murine dendritic Thy-1+ epidermal cell

Lymphoid cells with an affinity for the epidermis (epidermotropic lymphocytes) have been proposed to play a role in the immune functions of the epidermis. However, antigen-presenting Langerhans cells (LC) and indeterminate cells are presently the only cells in the human epidermis which have been demonstrated to originate in the bone marrow. Recent studies of murine epidermis have identified a population of bone marrow-derived cells which express Thy-1 antigen and which are present in a similar density to, but distinct from, LC. We therefore sought to identify the potential human analogue of the murine Thy-1+ epidermal cell utilizing a battery of antileukocyte reagents in immunohistochemical, flow cytometric, and cell sorting studies. A panel of antibodies failed to detect significant numbers of human Thy-1 antigen-bearing cells, T cells, B cells, monocytes/macrophages (other than LC), and natural killer cells in tissue sections, epidermal sheets, and epidermal cell (EC) suspensions. This was the case using EC suspensions either unfractionated or fractionated on Ficoll-Hypaque to enrich for leukocyte subpopulations. Since the nature of the murine Thy-1+ EC is uncertain, it is possible that antibodies directed against well-defined leukocyte subpopulations may not be of value in the detection of a potential human analogue. We therefore utilized double fluorescence staining with anti-HLe-1, an antibody which identifies all human leukocytes, and anti-HLA-Dr (Dr), which identifies epidermal LC, in order to demonstrate a potential population of HLe-1+ Dr- non-LC, bone marrow-derived cells. The vast majority of HLe-1+ cells were HLA-Dr+ LC; these were present at a density of 608 cells/mm2 in epidermal sheets. A minor population of HLe-1+ cells which did not express HLA-Dr (HLe-1+ Dr-) was observed in tissue sections, epidermal sheets, and EC suspensions. The nondendritic morphology and low density of these HLe-1+ Dr- EC in epidermal sheets (mean density of 4.2 +/- 1.6 cells/mm2) precluded their representing a strict human analogue of the murine Thy-1+ EC, since murine Thy-1+ EC are dendritic and are present in a density similar to that of LC. Purified preparations of the minor HLe-1+ Dr- EC population obtained by electronic cell sorting or panning and examined ultrastructurally were not enriched for any bone marrow-derived cell population. Thus, using currently available markers and sorting technology, we have been unable to identify a human analogue of the murine dendritic Thy-1+ epidermal cell.     

Thy-1阳性树枝状表皮细胞及郎格罕细胞的比较观察

观察了青、老年小鼠及大鼠不同部位皮肤内的Thy-1阳性树枝状表皮细胞(Thy-1⁺dEC)及郎格罕细胞(LC).于C57BL/6Ss小鼠,Thy-1⁺dEC通常比LC大;Thy-1⁺dEC的Thy-1抗原主要存在于细胞膜,而LC的Ia抗原较均匀分布,Thy-1⁺dEC突起常比LC短,有的甚至并不明显,正常角肮细胞表面也有少量Thy一抗原,但无Ia抗原.二种细胞于老年动物都少于青年动物.于Lewis/Ss及BN/Ss大鼠,未见到Thy-1⁺dEC.我们认为Thy-1⁺dEC可能具有免疫学功能.对人的Thy-1⁺dEC相应物的探索,也许能在皮肤病发病机理的研究中展开一条新的途径.     

Regional development of Langerhans cells and formation of Birbeck granules in human embryonic and fetal skin.

The regional development of Langerhans cells (LC) and the formation of Birbeck granules (BG) were examined in human embryonic and fetal skin. Samples were obtained from multiple anatomic sites and stained with anti-CD36, anti-CD1a, and anti-HLA-DR antibody as well as Lag antibody specifically reactive to BG and some vacuoles of human LC. In the first trimester, CD36+ dendritic epidermal cells were identified before the appearance of CD1a+ cells and Lag+ cells. Some of the former co-expressed HLA-DR antigens but not CD1a antigens. In the second trimester, regional variations in LC development were observed. Epidermal LC of palms and soles reached a peak in number in the first trimester but were rarely detected after 18 weeks estimated gestation age (EGA), whereas, in other regions, their number increased with age. In the second trimester, CD1a+ cells and Lag+ cells were also identified in the epidermis, although Lag+ cells appeared later than CD1a+ cells. The Lag+ cells until 17 weeks EGA showed a variety of staining intensities and immunoelectron microscopy revealed that they contained various amounts of Lag-reactive BG. Flow cytometric analysis showed that relative amounts of Lag antigens in LC increased during the second trimester and that fetal LC of 18 weeks EGA expressed the same amounts of HLA-DR, CD1a, and Lag antigens as did adult human LC. In the dermis, in the second trimester, numerous CD36+ cells and HLA-DR+ cells were found, whereas CD1a+ cells and Lag+ cells were rarely detected. Taken together, it is suggested that HLA-DR+ dendritic cells acquire CD1a+ antigens first and then form BG after migration to the epidermis and that fetal LC are phenotypically mature in the second trimester.     

Characterization of cutaneous infiltrates in MRL/lpr mice monitored from onset to the full development of lupus erythematosus-like skin lesions.

The skin is a primary site injured in lupus erythematosus (LE), but it is still controversial whether the injury is due to cells of the mononuclear infiltrate and which immunocompetent cells play the major role in the development of cutaneous LE. To better characterize the role of immunocompetent cells, we performed an immunohistochemical examination of these cells in LE-like skin lesions in MRL/Mp-lpr/lpr (MRL/lpr) mice. Skin lesions in 60 female MRL/lpr mice were monitored from onset to full development. Skin specimens from each stage were stained for epidermal Ia+ Langerhans cells (Ia(+)-LC), for Thy-1+ dendritic epidermal cells (Thy-1+DEC), and for the phenotype of the mononuclear cell infiltrates. The numbers of Ia(+)-LC and Thy-1+DEC were decreased markedly in the skin lesions at the later stage. However, the numbers of Ia(+)-LC were increased significantly in the central portion of lesions at an early stage and in the peripheral portion of lesions later. L3T4+ cells were predominant, and the L3T4/Lyt-2 ratio was high in dermal infiltrates at an early stage. With advancing stage, the L3T4/Lyt-2 ratio gradually decreased in dermal infiltrates, whereas the Thy-1.2/Lyt-2 ratio in lymph nodes was reversed. L3T4+ cells were especially predominant in dermal infiltrates under the epidermis with increased numbers of Ia(+)-LC. This immunohistochemical analysis of a mouse model of cutaneous LE revealed changes in immunocompetent cell populations with the evolution of skin lesions, and we conclude that Ia(+)-LC and Thy-1+DEC, as well as L3T4+ and Lyt-2+ cells, may play pathogenic roles in the development of skin lesions.     

Thy-1+ dendritic epidermal cells undergo mitosis in vivo

Recently, morphologic evidence that epidermal Langerhans cells (ELC) undergo a mitotic cycle in normal mouse ear skin has been presented. In the present study, using immunohistochemical staining, we examined the mitotic activity of Thy-1-positive dendritic epidermal cells (Thy-1+DEC) in the normal murine epidermis. A small number of Thy-1+DEC showed round, cleaved, paired, and paired dendritic morphologies, which are identical to those occurring during ELC mitosis. We conclude that normal Thy-1+DEC undergo mitosis within the epidermis to maintain their population in the murine epidermis.     

Surface densities of murine Ia+ dendritic epidermal cells (Ia+DECs) and Thy-1+ dendritic epidermal cells (Thy-1+DECs) in relationship to aging and ultraviolet B (UVB) radiation

Identification and enumeration of both Ia + dendritic epidermal cells (Ia + DECs) and Thy-1 + dendritic epidermal cells (Thy-1 + DECs) from various parts of the body and non-irradiated and ultraviolet B (UVB) irradiated back skin were examined using epidermal sheets of C3H/He inbred mice of different age groups and indirect immunofluorescent technique. The following results were obtained: [1] There was a significant decline in both Ia + DEC and Thy-1 + DEC density in the mice in the oldest group (48–50 weeks); [2] The densities of Ia + DECs were significantly higher than those of Thy-1 + DECs in comparisons of various parts of the body; [3] At 24 h after 60–120 mJ/cm² UVB irradiation, the Ia + DECs and Thy-1 + DECs decreased significantly in a dose-dependent fashion. The Ia + DECs decreased drastically (p<0.01) while the Thy-1 + DECs decreased mildly (p<0.05). [4] The degree or resistance to UVB differed between Ia + DECs and Thy-1 + DECs in older mice (40–48 weeks). These findings may imply that the decline of the Ia + DECs and Thy-1 + DECs reflects alterations in immune response during aging; As do Ia + DECs, Thy-1 + DECs might also play a role in UVB induced specific unresponsiveness in contact hypersensitivity; each type of Ia + DECs and Thy-1 + DECs follows a distinct biological kinetic pattern after UVB irradiation.     

Changes in expression of Ia, Thy-1, and Ly-5 antigens in epidermal cells during delayed contact sensitivity reactions in mice: flow cytometric analysis

Ia antigen-bearing (Ia+) Langerhans cells have attained an important position as immunocompetent cells in the epidermis. Recently there have been successive reports on other new possible candidates for immunocompetent cells in the epidermis, i.e., Ia+ keratinocytes and dendritic Thy-1 antigen-bearing (Thy-1+) epidermal cells which also express Ly-5 antigen and asialo-GM1. Based on our previous findings that in allergic contact sensitivity reactions, keratinocytes express Ia antigen 3-9 days postchallenge, in this report, we have attempted to define more clearly the dynamic changes of Ia+ keratinocytes and dendritic Thy-1+ epidermal cells by enumeration of the precise percentages of Ia+, Thy-1+, and Ly-5 antigen-bearing (Ly-5+) cells in epidermal cells at various times of the challenge phase in allergic contact sensitivity reactions by use of a fluorescence-activated cell sorter. By 24 h postchallenge, the percentages of Ia+, Thy-1+, and Ly-5+ cells showed hardly any change. There were approximately 2% Ia+ cells, 50% Thy-1+ cells which consist of 2 populations (i.e., 45% weakly Thy-1 antigen-positive cells and 4% strongly Thy-1 antigen-positive cells), and 3.5% Ly-5+ cells. From 48 h postchallenge, however, the percentage of Ia+ cells and that of Thy-1+ cells began to increase and reached a plateau, with approximately 20% Ia+ cells and 70% Thy-1+ cells, respectively, at 120 h postchallenge. The change of the percentages of Ly-5+ cells appears to correspond to that of strongly Thy-1 antigen-positive cells. Only at 48 h postchallenge, Ly-5+ cells and strongly Thy-1 antigen-positive cells showed a small increase in number, comprising approximately 10% of the epidermal cells. These data suggest that among Thy-1+ epidermal cells, strongly Thy-1 antigen-positive cells correspond to dendritic Thy-1+ epidermal cells, and in contact sensitivity reactions in mice, dendritic Thy-1+ epidermal cells show only a minor dynamic change in contrast to Ia+ cells, in which more than 15% of keratinocytes express Ia antigen from 48 h postchallenge.     

Rapid induction of Thy-1 antigenic markers on keratinocytes and epidermal immune cells in the skin of mice following topical treatment with common preservatives used in topical medications and in foods

Earlier experiments from our laboratory revealed that the medication most commonly used for depigmenting patients with vitiligo, monobenzyl ether of hydroquinone (MBEH), when applied to the skin of DBA/2 mice caused an increase in the population density (cells/mm2) of identifiable Ia+ and ATPase+ Langerhans cells. Further, this increase in Langerhans cell density could be correlated with an increase of contact hypersensitivity (CHS) reactivity to dinitrofluorobenzene (DNFB). The current experiments demonstrated that other compounds chemically similar to MBEH, such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), which are used as preservatives/antioxidants in many topical medications, cosmetics, food, and rubber products, can in five days significantly increase the population density of Thy-1+ dendritic epidermal cells. These compounds had no effects on Ia+ cells. This observation suggests that the Thy-1+ DEC cells may be more mobile and/or their surface markers may be readily expressed and are not a slowly mobile (trafficking) population of cells as suggested by the results of previous work. In addition, these parasubstituted phenolic compounds behaved like pertussis toxin and induced Thy-1 and Ia expression on keratinocytes. These changes in Thy-1 immune markers were not accompanied by functional alterations in the immune response to contact allergens as measured by the ear swelling technique.     

Identification of an equivalent to murine Thy-1+ dendritic epidermal cells in the rat epidermis.

In the murine epidermis, there exist Thy-1+ dendritic epidermal cells (Thy-1+DEC). These cells are Thy-1+, CD45+, CD3+ and asialo GM1+ but CD5-, CD4-, CD8-, or Ia-1-, and express T cell receptor (TCR) gamma delta. Recently, most of these TCR gamma delta of Thy-1 DEC are shown to consist of a V gamma 3-V delta 1 combination. There has been no evidence that the same type of cell population exists in other species except mice. In this study, we investigated the existence of a Thy-1+DEC equivalent in the rat epidermis. The epidermal sheets obtained from rats were stained with various monoclonal antibodies to rat lymphocytes. We developed a monoclonal antibody (1F4) to rat CD3 complex. 1F4 stained thymocytes and peripheral T cells and also immunoprecipitated T cell receptor with CD3 complex. Using 1F4 and a recently developed monoclonal antibody to rat TCR alpha beta, we could identify dendritic CD4-, CD8-, CD5-, CD3+, TCR alpha beta- cells in the rat epidermis. These CD3+, TCR alpha beta- cells are strong candidates as an equivalent to TCR gamma delta + murine Thy-1+ DEC.     

Phenotypic heterogeneity and cytotoxic activity of Con A and IL-2-stimulated cultures of mouse Thy-1+ epidermal cells

Short-term and long-term cultures of mouse Thy-1+ epidermal cells (EC) were established in order to characterize their phenotypic and functional properties. Concanavalin A (Con A) and Interleukin 2 (IL-2) stimulated Thy-1+ EC mediated non-MHC directed cytotoxicity preferentially against the NK-sensitive target, YAC-1 vs the NK-resistant target, P815; these cells also mediated antibody-dependent cell-mediated cytotoxicity (ADCC), indicating the presence of IgG-FcR on at least some of them. Freshly isolated Thy-1+ EC failed to lyse YAC-1 targets; however, this activity was observed after 9 d of culture with Con A and IL-2. While dendritic Thy-1+ EC, in vivo, do not express the T-cell markers, L3T4 and Lyt-2, short-term cultured cells displayed phenotypic heterogeneity with small but significant percentages of Lyt-2+ and L3T4+ cells appearing transiently. The phenotype of the effector cell(s), which mediates cytotoxic activity, was determined by utilizing flow cytometry to sort short-term cultured EC into positively and negatively stained populations. Cells which express L3T4, or which lack asialo GM1, did not lyse YAC-1 targets; maximum cytotoxic activity was found within populations of cells which are asialo GM1+, Lyt-2-, and asialo GM1+, Lyt-2+. These studies indicate that Thy-1+ cells derived from mouse epidermis when cultured in the presence of Con A and IL-2 have the capacity to generate a phenotypically heterogeneous population, some cells of which are capable of mediating cytotoxic activities.     

Freshly isolated Thy-1+ dendritic epidermal cells express T cell receptor gamma delta-CD3

Within murine epidermis exists a population of Thy-1+ DEC which express membrane Thy-1 antigen, but lack CD8 or CD4 antigen. We examined freshly obtained non-cultured Thy-1+ DEC both by immunofluorescence and by biochemical techniques to identify the protein products of the T cell receptor (TCR) and the associated CD3 complex on these cells. Virtually all of the Thy-1+ DEC are brightly positive in CD3 expression with immunofluorescence using the monoclonal antibody 145-2C11. By immunoprecipitation, using this same antibody and polyclonal anti-TCR-gamma antibody, the only TCR heterodimer detected on the freshly isolated Thy-1+ DEC is the gamma delta heterodimer. These findings suggest that in the phenotype and TCR expression, Thy-1+ DEC are analogous to CD8-, CD4- early fetal thymocytes.     

Disparate effects of in vitro low-dose UVB irradiation on intravenous immunization with purified epidermal cell subpopulations for the induction of contact hypersensitivity

Low-dose ultraviolet (UV) B irradiation suppresses contact hypersensitivity (CH) reactions and alters the antigen-presenting function of epidermal cells (EC) in mice. To identify the EC sources of immunosuppression in this system, we examined the effect of UVB on the capacity of EC to induce and to regulate CH to trinitrochlorobenzene (TNCB). On day 0, cell sorter-purified populations of Ia+EC, Thy-1+EC, or Ia-/Thy-1-EC from CBA and C3H/HeJ mice were exposed to 200 J/m2 UVB from unfiltered FS20 Sunlamps, derivatized with hapten, and inoculated intravenously into syngeneic mice (5000 cells per inoculum). After 6 d, responsiveness was tested by challenging the left ear with 2% TNCB and measuring ear swelling responses. On day 14, regulation was tested by painting 7% TNCB on abdominal skin; after 6 d the right ear was challenged. Whereas mice which received haptenated unirradiated Ia+EC exhibited full CH responses without down-regulation, mice inoculated with haptenated irradiated Ia+EC displayed significantly diminished primary responses and, on subsequent immunization, displayed down-regulation. On the other hand, panels of mice that received haptenated unirradiated Thy-1+EC, and haptenated irradiated Thy-1+EC both showed hyporesponsiveness as well as down-regulation. Intravenous immunization with haptenated unirradiated Ia-/Thy-1-EC or with haptenated irradiated Ia-/Thy-1-EC led in each instance to immunologically "null events." These findings indicate that UVB irradiation profoundly affected Ia+EC such that their capacity to sensitize for CH was not only abrogated, but that such treatment also resulted in down-regulation of CH responses. By contrast, the same phototreatment had no effect on the inherent property of Thy-1+EC to mediate down-regulation of CH. We conclude that Ia+EC are immunologically relevant targets of low-dose UVB radiation, and that two populations of irradiated EC, Ia+EC, and Thy-1+EC, have the potential to deliver down-regulatory signals in this model of immunosuppression.     

Thy-1+ dendritic epidermal cells in mice: precursor frequency analysis and cloning of concanavalin A-reactive cells

Bulk cultures of mouse Thy-1+ dendritic epidermal cells (Thy-1+ DEC) have been shown to proliferate in response to concanavalin A (Con A) and IL-2, to secrete IL-2-like growth factors, and to lyse target cells such as YAC-1. Limiting dilution microculture was utilized in order to determine the precursor frequency of Con A-responsive Thy-1+ DEC in suspensions of AKR/J epidermal cells as well as whether these several functional activities all reside within a single Thy-1+ DEC precursor. Precursor frequency analysis of cultures established with limiting numbers of FACS-purified Thy-1+ DEC, irradiated syngeneic splenic filler cells and exogenous IL-2 indicated that approximately 20% of Thy-1+ DEC proliferated in response to Con A. Parallel microcultures in which purified Thy-1+ DEC were plated at a density of 0.5 cells/well were used to establish clones. Twenty clones were characterized phenotypically, and ten of these were also tested for their capacities to proliferate in response to Con A or IL-2, to secrete IL-2-like growth factors, and to exhibit cytotoxicity. All clones were Thy-1+ and L3T4-, but while most were also Lyt-2-, several contained 3%-18% dull Lyt-2+ cells. Functional studies revealed that each clone displayed all of the above functional activities, albeit with substantial quantitative variation. Clones with the highest cytotoxic activity had relatively low responsiveness to Con A or IL-2 and included all clones containing dull Lyt-2+ cells; conversely, clones with the highest proliferative responses had relatively low cytotoxic activity and were all Lyt-2-. This degree of functional and phenotypic heterogeneity among cloned Thy-1+ DEC may reflect their particular states of activation or differentiation; whether it reflects the biologically relevant in vivo activities of these cells must still be determined.     

Expression of the Ly-5 alloantigenic system on epidermal cells

The expression of Ly-5 alloantigens is confined to hemopoietic cell types and is therefore considered a valuable indicator for the bone marrow derivation of a given cell. The further finding that different hemopoietic cell lineages express different molecular forms of the Ly-5 alloantigens prompted us to investigate (1) whether murine epidermal cells or subpopulations thereof express Ly-5 specificities and if so, (2) whether the expression of particular molecular configurations of Ly-5 antigens would allow us to gain a clue about the derivation of certain epidermal cell populations. When epidermal sheets from BALB/c, C57Bl/6, and C3H/He mice, were exposed to monoclonal anti Ly-5.1 antibody in an indirect immunofluorescence technique, a system of evenly distributed, dendritic cells was visualized. Allelic exclusion of the Ly-5 system was demonstrated by replacing anti-Ly-5.1 antibody by anti-Ly-5.2 reagent and by using epidermal sheets from SJL/J mice. Studies on epidermal cell (EC) suspensions revealed that about 1.6-5.2% of C3H/He EC were Ly-5-reactive and that approximately equal numbers of Ly-5-positive cells bore either Thy-1 or Ia antigens. Electron microscopic studies disclosed two morphologically different Ly-5-positive cell populations, i.e., cells of the Langerhans cell lineage and a recently defined cell system, whose most prominent feature is the expression of the Thy-1 antigen. We have termed these cells dendritic Thy-1+EC (dTHY-1+EC). In order to define the molecular configurations of the Ly-5 alloantigens, EC and spleen cells were internally labeled and--after immunoprecipitation of cell-membrane detergent extracts with anti-Ly-5.1--were analyzed on sodium dodecyl sulfate-polyacrylamide gels. Spleen cells yielded 3 bands with a molecular weight of 180,000, 195,000, and 215,000, respectively, as is characteristic for T lymphocytes, non-T/non-B cells, and B lymphocytes. In contrast, a single 195,000-200,000 dalton band was found in precipitates of both untreated and Langerhans cell-depleted (anti-Ia+C) EC. These data demonstrate the existence and active biosynthesis of the Ly-5 alloantigenic system on certain EC populations, i.e., Langerhans cells and dThy-1+EC, and therefore imply that both cell types originate from a bone marrow-derived precursor. The expression of the same molecular configuration of Ly-5 alloantigens on both LC and dThy-1+EC suggest that these two cell populations do not belong either to the T-cell or to the B-cell lineage and imply an ontogenetic relationship between dThy-1+EC and Ia-positive EC.     

FACS purification of bone marrow-derived epidermal populations in mice: Langerhans cells and Thy-1+ dendritic cells

A method was developed which allows for the separation and purification of Langerhans cells (LC) and Thy-1+ cells (Thy-1+dEC) from mouse epidermis. Epidermal cell (EC) suspensions were subjected to Ficoll separation, and the resulting interface EC were harvested. These EC were then "tagged" with the appropriate monoclonal antibody and sorted into positive and negative populations using the Fluorescence Activated Cell Sorter (FACS). Preparations of viable LC and Thy-1+dEC were obtained with 94-98% and 94-99% purities, respectively.     

Langerhans cell migration into ultraviolet light-induced squamous skin tumors is unrelated to anti-tumor immunity.

There has been much speculation as to the role of Langerhans cells (LC) in the induction of anti-tumor immunity. Whereas there is considerable circumstantial evidence that disruptions in the density and function of these cells during the early stages of ultraviolet (UV) light- and chemical carcinogen-induced carcinogenesis may be important for enabling developing neoplasms to escape immune destruction, the role of the large number of these cells found infiltrating developed skin tumors is less clear. To investigate this we have compared the LC density infiltrating transplanted non-immunogenic and immunogenic UV-induced murine tumors as well as LC in the epidermis overlying the tumors. Whereas two non-immunogenic tumor lines attracted large numbers of Ia+ dendritic cells, an immunogenic tumor line did not. Similar results were obtained whether the tumors were transplanted into syngeneic immunocompetent or athymic immunodeficient mice. Hence, there was no relationship between tumor immunogenicity or host immunocompetence and Ia+ dendritic cell density. Furthermore, there was no correlation with the pattern of T-cell infiltration of the tumors or CD4/CD8 cell ratio. Our results also indicate that whereas UV light decreased Ia+ cell density, both in the epidermis and the tumors, it did not inhibit the tumors from attracting Ia+ dendritic cells. Thus, the Ia+ dendritic cells infiltrating skin tumors are unlikely to indicate a host immune response to the tumor, but are more likely to be attracted by tumor-derived cytokines.     

小鼠Thy-1阳性树突状表皮细胞密度的两性差别

现已证实在小鼠不同品系下同部位Thy-1阳性树突状表皮细胞(Thy-1⁺dEC)密度存在明显差异.至今尚无有关其两性间差别的报道.     

An immunohistochemical and immunoelectron microscopic study of the ontogeny of rat Langerhans cell lineage with anti-macrophage and anti-Ia monoclonal antibodies

An immunohistochemical study with anti-macrophage and anti-Ia monoclonal antibodies was performed to clarify the relationship between Langerhans cells (LC) and indeterminate cells (IC) in rat epidermis both in adulthood and in the fetal stage. On immunoelectron microscopy, a mouse anti-rat macrophage monoclonal antibody, TRPM-1, recently produced by us, reacted with IC and some LC in adult rat skin. Ontogenic study revealed that TRPM-1-positive cells first appeared in the epidermis of fetal rat heads on Day 17 of gestation and then spread caudally along the anterior-posterior axis. On Day 20 of gestation, when the distribution of the TRPM-1-positive cells over body surface became even, Ia-positive cells appeared in the epidermis and began to increase in number. Ia-positive cells with Birbeck granules were found on Day 21 of gestation. These results indicate that. TRPM-1-positive IC matured into Ia-expressing LC after being exposed to microenvironmental change during the perinatal period. The number of Ia-positive cells exceeded that of TRPM-1-positive cells at around 5 d after birth. Afterwards, there were more dendritic Ia-positive cells found in the interfollicular areas than TRPM-1-positive ones. However, local concentrations of the TRPM-1-positive IC in the follicular infundibula were frequently found in the fetal stage and occasionally in adulthood. These TRPM-1-positive cells in the follicular infundibula were thought to be a precursor pool in the epidermis for LC.