Enrichment of human epidermal Langerhans cells by attachment to erythrocyte monolayers

Rapid purification of human Langerhans cells using paramagnetic microbeads

Detailed studies on the biology of Langerhans cells (LC), which account for only 1-3% of all epidermal cells, require isolation from their cutaneous symbionts. Several techniques of LC isolation have been reported, including positive enrichment with mAb coupled to immunomagnetic beads. The disadvantage of this technique is the size of the beads (approximately 2-5 microns), which can interfere with subsequent phenotypic and functional analyses. This limitation prompted us to test whether paramagnetic microbeads (15 nm) employed by the MACS system could be used to purify LC from human skin. To isolate fresh LC (fLC), epidermal cell suspensions (EC) were stained with anti-CD1a mAb and with appropriate secondary reagents conjugated to microbeads and to FITC. They were then passed over a separation column and exposed to a strong magnetic field. Thereafter both CD1a-depleted and CD1a-enriched cells were collected. Cultured LC (cLC) were isolated by staining 72-h cultured EC with anti-HLA-DR mAb followed by the same isolation procedure. Using this technique, we could routinely isolate viable EC that were 45-88% CD1a+ or HLA-DR+ as determined by FACS. Two-color FACS analysis demonstrated the majority of MACS-purified cells to be CD1a+/HLA-DR+, indicating that they were indeed LC. By transmission electron microscopy (TEM), the MACS-purified CD1a+/HLA-DR+ cells showed typical ultrastructural characteristics of LC. Furthermore, MACS-purified fLC or cLC were functionally intact, because they stimulated the proliferation of alloreactive T cells in a primary, one-way, mixed epidermal cell leukocyte reaction (MECLR). We conclude that MACS-separation is an efficient and rapid method to isolate human fLC and cLC of high purity and unimpaired function.

Adhesion of epidermal Langerhans cells to keratinocytes mediated by E-cadherin

Langerhans cells (LC) are the principal accessory cells present in epidermis. Because LC have limited capacity for self-renewal, epidermis is continually repopulated by as-yet uncharacterized bone marrow-derived LC progenitors. In addition, although LC persist in epidermis for extended periods, LC are induced to migrate from skin to regional lymph nodes after antigen exposure. To begin to elucidate mechanisms involved in LC trafficking, we characterized LC-keratinocyte (KC) interactions. Here we report that fresh murine LC express cadherins, and that LC adhere to KC in vitro through E-cadherin. Cultured LC (which may bear a phenotypic and functional relationship to LC that have migrated to lymph nodes) express lower levels of E-cadherin and exhibit decreased affinity for KC. These results suggest that expression of E-cadherin by LC promotes persistence of these cells in epidermis, and that cadherins may play important and unanticipated roles in interactions between leukocytes and epithelia.

Effective enrichment of murine epidermal Langerhans cells by a modified(mismatched) panning technique

A method for the enrichment of murine epidermal Langerhans cells (LC) is described in detail. It is based on positive selection of LC from pre-enriched fresh or cultured epidermal cell suspensions derived from ear skin by a modified panning technique. The method uses the interspecies cross-reactivities of anti-immunoglobulin antibodies: when LC in an epidermal cell suspension are labeled with mouse anti-major histocompatibility complex (MHC) class II antibodies they bind to petri dishes coated with anti-rat immunoglobulin antibodies. We therefore call this method "mismatched panning." After rinsing off non-adherent cells, the adherent LC can easily be dislodged by adding excess amounts of rat immunoglobulins, which effectively compete with the LC-bound mouse anti-MHC class II antibodies for binding to the petri dish. Using this modified panning technique, both fresh and cultured LC could be enriched up to more than 90% purity. From one ear, 2.0-3.0 x 10(4) fresh LC and 3.0-4.5 x 10(4) cultured LC could be obtained. Of all LC present in a primary, unenriched epidermal cell suspension, 40-60% were recovered when panned immediately after isolation of the epidermal cells and 50-75% when panned after 3 d of epidermal cell culture. Viability of panned LC was consistently more than 90%. Antigen presenting and T-cell-stimulating capacity of LC and responses to the cytokines granulocyte/macrophage colony-stimulating factor and tumor necrosis factor-alpha were not impaired by this panning procedure. The major advantage of this method compared to pre-existing panning techniques is the ease with which adherent LC can be dislodged from the panning dishes. Because the elution procedure is very gentle, virtually all panned LC are viable. As a consequence, good yields of highly enriched LC can be obtained in a reasonable time.

Effects of Ultraviolet Radiation on Murine Epidermal Langerhans Cells: Doses of Ultraviolet Radiation that Modulate ICAM-1 (CD54) Expression and Inhibit Langerhans Cell Function Cause Delayed Cytotoxicity In Vitro

Low doses (100 J/m2) of ultraviolet B (UVB) radiation from sunlamp fluorescent FS20 tubes inhibit the ability of freshly isolated murine epidermal Langerhans cells (LC) to support anti-CD3 MoAb-induced T-cell mitogenesis and selectively inhibit the upregulation of ICAM-1 expression by LC without causing appreciable cytotoxicity in short-term (less than or equal to 24 h) incubations (J Immunol 146:3347-3355, 1991). In the present study, epidermal cells (EC) were exposed to UVB radiation or were sham-irradiated and cultured for 24, 48, or 72 h when LC were recovered, enumerated, and assayed for simultaneous expression of I-A antigens and ICAM-1 by flow cytometry. UVB-irradiated LC that had been cultured for 24 h exhibited levels of I-A antigens comparable to those on unirradiated LC but expressed substantially less ICAM-1. After 48 and 72 h, cultured UVB-irradiated LC expressed somewhat lower levels of I-A antigens and markedly less ICAM-1 than unirradiated controls. Although similar numbers of LC were recovered from cultures initiated with UVB-irradiated and unirradiated epidermal cells after 24 h, far fewer identifiable LC were recovered from cultures seeded with irradiated cells at 48 and 72 h (approximately 50 and approximately 10% of control, respectively). The effect of UVB radiation on the survival of LC in vitro was not reversible with exogenous TNF alpha (125 U/ml) alone or granulocyte/macrophage colony-stimulating factor (5 ng/ml) and IL-1 (50 U/ml) in combination, although these cytokines had modest effects on the expression of I-A antigens and ICAM-1 by cultured UVB-irradiated LC. Results of survival studies performed with enriched LC preparations demonstrated that UVB radiation was clearly cytotoxic for LC and did not merely downregulate surface expression of I-A antigens or alter LC buoyant density. Exposure of LC to radiation from blacklight fluorescent (UVA) tubes (0.25 J/cm2) in the presence of 8-methoxypsoralen (1 micrograms/ml; PUVA) or monochromatic UVC radiation (20 J/m2) also inhibited LC accessory cell function. Results of survival studies performed with EC that had been exposed to PUVA or UVC radiation before culture were similar to those of studies performed with UVB-irradiated cells, although PUVA- and UVC-induced LC cytotoxicity was much more pronounced 48 h after culture initiation than UVB-induced cytotoxicity. UVA radiation alone augmented LC recovery at 24 and 48 h, but did not influence I-A antigen or ICAM-1 expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Flow cytometry analysis of adhesion molecules on human Langerhans cells

The Langerhans cell (LC) migrates between the epidermis and the regional lymph nodes to present antigens. This migration pattern requires the expression of a changing repertoire of cell-surface molecules. In this work, we have investigated the expression of the adhesion molecules CD 11/CD 18 and CD 58 on LCs. Human epidermal cell suspensions were enriched in LCs (mean enrichment 75%) using a two-step technique including a Ficoll-Hypaque gradient followed by Fc receptor panning with IgG-coated sheep erythrocytes. The number of cells obtained per experiment was 750,000 (extremes 280,000-1,800,000), and the following antibodies were tested on fresh suspensions and/or after 48 hours in culture: BB3 (antithyroglobulin negative control IgG2a), OKT6 (anti CD1a, Ortho), anti HLA-DR (Becton-Dickinson), MHM 24 (anti CD 11a, leukocyte typing workshop n(0)3), MO1 and 44 (anti CD 11b, leukocyte typing workshop n(0)3), anti CD 11c (Immunotech), 60.3 and MHM 23 (anti CD 18, leukocyte typing workshop n(0)2), TS2/9.1.1 (anti CD 58, leukocyte typing workshop n(0)3). We found that amongst CD 11 subunits, only CD 11c was expressed in fresh suspensions, but was weaker than CD 18, and disappeared with culture. CD 58 was not detected in fresh suspensions but appeared after 2 days of culture, confirming earlier work. Thus the LC exhibits cell surface characteristics similar to tissue macrophages (CD 18 and CD 11c) prior to culture. The expression of CD 58 after culture is in accordance with the interaction of LC with CD2 bearing T-lymphocytes during antigen presentation in peripheral lymph-nodes.

Isolation of epidermal Langerhans cells

Langerhans cells (LC) play an important role in the skin immune system. They are bone marrow-derived and function as the only accessory and antigen-presenting cells in the skin. Several techniques for enriching these cells have been devised, and four, including density gradient centrifugation, use of cell sorter, panning and immunomagnetic separation, are discussed. It is concluded that the most satisfactory method for isolation of LC is based on density gradient centrifugation and the most satisfactory for depletion of epidermal cell preparations for LC is based on the immunomagnetic principle.

Enrichment of unlabeled human Langerhans cells from epidermal cell suspensions by discontinuous density gradient centrifugation

In this report we introduce an alternative procedure for enrichment of human epidermal Langerhans cells (LC) from epidermal cell suspensions of normal skin. By means of discontinuous Ficoll-Metrizoate density gradient centrifugation, a fraction containing high numbers of viable, more than 80% pure LC was recovered, as judged by CD1a expression. The purity of the LC-enriched fraction appeared to be dependent on the percentage LC in the crude epidermal cell suspension. LC enriched by this method retained their accessory and antigen-presenting capacities, as determined in the Concanavalin-A induced T-cell response, in the allogeneic mixed leukocyte reaction and in the antigen-specific T-cell proliferation assay in vitro. The great advantage of this method is that it is simple and rapid and that the isolated LC are unlabeled.

Immunostimulatory capabilities of highly enriched Langerhans cells in vitro

Langerhans cells (LC) are epidermal antigen-presenting cells capable of inducing allogenic, antigen-specific, and cytotoxic T cell proliferation. Previous studies have examined the dynamics of LC maintained in vitro in crude epidermal cell (EC) suspensions in which the major cell type is the keratinocyte (KC). To avoid the confounding effects of KC and other immunoregulatory cells on LC dynamics in vitro, highly enriched murine LC (85%) were studied, through 72 h of incubation in vitro, for their ability to present alloantigen (in a primary allogenic proliferation assay) and foreign antigen (in a secondary autologous proliferation assay). The results were compared to similar studies using crude EC suspensions. Freshly prepared LC are very poor stimulators of a primary allogenic proliferation response, with a 12- to 16-fold increase in stimulatory capacity by 72 h using panned-enriched and crude EC suspensions, respectively. Similarly, freshly prepared LC are weak stimulators of a secondary autologous proliferation response, with a 2.5- to 6-fold increase in immunostimulatory capability by 72 h. The overall increased stimulatory effect observed with the crude EC suspensions compared to highly enriched LC is most likely attributed to the effect of KC on T cell proliferation, rather than to a maturation effect of KC on LC during the 72 h of in vitro incubation. Using back-scattered electron imaging, the surface density of MHC-class II molecules (Ia) increased three- to fourfold through culture, which parallels the increase in functional ability. This study demonstrates that LC in either a crude or highly enriched cell suspension mature into potent immunostimulatory cells after incubation in vitro with an increased surface expression of Ia molecules. Keratinocytes are not necessary for LC maturation in vitro, but seem to exert some stimulatory effect by enhancing lymphocyte proliferation in the functional assay system.

Langerhans cell- and T-lymphocyte functions in patients with atopic dermatitis with disseminated cutaneous herpes simplex virus infection

We studied whether Langerhans cell (LC)- and T-lymphocyte functions of atopic dermatitis (AD) patients are impaired. Our study groups consisted of 6 patients with AD with previous disseminated herpes simplex virus infection (AD + HSV), 8 patients with ordinary AD, and 5 healthy subjects. Suction blisters were performed on abdominal skin and LC isolated on the basis of their attachment to IgG-coated erythrocyte monolayers. Antigen-presenting function of purified LC was studied by measuring the proliferation of HSV-stimulated T cells. Langerhans cells were also used to stimulate T cells in autologous mixed cell reaction (AMCR). In addition, the production of epidermal cell thymocyte-activating factor (ETAF) by crude epidermal cells was measured. The HSV-induced T-cell proliferation in AD + HSV and AD patients was comparable with that of controls. The AMCR responses of patients with AD + HSV and AD were clearly diminished when compared with healthy controls. Patients with AD also produced significantly less ETAF than controls. Our results suggest that HSV antigen-presenting function of LC from patients with AD + HSV seems to be intact. Defective AMCR may reflect an abnormality in autoregulation and generation of effector cells and this together with decreased ETAF production may have pathogenetic significance in AD.

Human epidermal Langerhans cells and peripheral blood monocytes. Accessory cell function, autoactivating and alloactivating capacity and ETAF/IL-1 production

We compared the functional capacities of human epidermal Langerhans cells (LC) and peripheral blood monocytes. Epidermal sheets were obtained by a suction blister device. After enzymatic treatment LC were enriched by attaching them to IgG-located erythrocyte monolayers. On a per cell basis, LC were several times more efficient accessory cells than monocytes in augmenting nickel-and tuberculin (PPD)-induced T-cell proliferation. In mixed cell cultures LC stimulated both autologous and allogeneic T cells, whereas monocytes stimulated only allogeneic cells. In addition, LC were significantly more potent allogeneic stimulators than monocytes. Although monocytes were weaker accessory cells and allogeneic stimulators than LC, they induced higher interleukin 1 (IL-1) activities than LC-enriched or LC-depleted cells. These results indicate that there are functional differences between LC and monocytes and that antigen presentation and mediator secretion are not correlated.