Enrichment of human epidermal Langerhans dendritic cells

Enrichment of unlabelled human Langerhans cells by modified discontinuous Ficoll-metrizoate density medium and following Langerhans cell culture

Highly enriched and specifically unlabelled human Langerhans cells (LC) from epidermal cell suspensions (ECS) are indispensable for the intensive study of LC function. Discontinuous Ficoll-metrizoate density gradient centrifugation was found to be a satisfactory method of enriching LC from ECS. In contrast to a previous study, however, the majority of LC floated on Ficoll-metrizoate with a density of 1.057 g/cm3 instead of 1.068 g/cm3. The concentration of unlabelled LC can be enriched to as high as 92% from the original 1.8-3.1% LC in ECS. Approximately 40-50% of original LC can be harvested. The procedure was also simplified by using a Schick razor instead of a dermatome to obtain thin epidermal sheets (about 0.25 mm in thickness), omitting the density gradients of 1.089 and 1.10 g/cm3 and using the avidin-biotin complex method to identify LC. LC are non-proliferative cells in in vitro culture systems. The viability of LC dropped to 20-30% after 3 days in the culture medium. It was also observed that LC tended to attach to aggregated keratinocytes in the culture system.

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.

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.

Removal of Langerhans cells from human epidermal cell suspensions by immunomagnetic particles

The possibility of eliminating the class II antigen-expressing and antigen-presenting Langerhans cells from normal human epidermal cell suspensions was investigated. Cell suspensions containing 1.7-2.8% Langerhans cells were prepared by enzyme treatment of human skin obtained at plastic surgery. The cells were incubated with mouse monoclonal antibodies directed against the CD1 antigen present on Langerhans cells and were further incubated with magnetic particles, 4.5 micron in diameter, coated with sheep anti-mouse IgG. The optimal ratio between particles and target cells was found to be 40:1. The rosetted Langerhans cells were removed by a cobalt-samarium magnet. In six experiments immunoperoxidase staining revealed 0-0.1% (mean 0.03%) CD1-reactive Langerhans cells in the depleted cell fraction. The alloantigen presenting capacity of the depleted cell fraction, measured by [3H]thymidine incorporation, was abolished.

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.

Enrichment of human epidermal Langerhans cells by attachment to erythrocyte monolayers

The present investigation introduces a method for purification of human epidermal Langerhans cells (LC). The method is based on the attachment of LC to IgG-coated sheep erythrocyte monolayers via their Fc receptors. To optimize the enrichment assay, several variables were tested. The best results were obtained when epidermal cells were centrifuged against erythrocyte monolayers; the purification procedure was performed at 4 degrees C in the presence of 5% fetal calf serum, using about 6 X 10(6) epidermal cells per erythrocyte plate (diameter 5 cm). The average purity of the recovered LC was 80.9% and LC-depleted fractions contained an average of 0.5% DR-positive cells. LC were able to enhance significantly leukoagglutinin- and purified protein derivative-induced T lymphocyte proliferation and leukocyte migration inhibitory factor production.

The role of Langerhans cells in antigen presentation

Epidermal Langerhans cells are dendritic bone marrow-derived cells which synthesize and express Ia antigens. During the past decade, in vitro studies have demonstrated that they play a critical role in the induction of many types of T-cell responses. Specifically, Langerhans cells are effective antigen-presenting cells in allogeneic and antigen specific proliferative and cytotoxic T-cell responses. This paper reviews these functions and suggests areas of future investigations into the mechanisms involved in T-cell activation by Langerhans cells.

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.

Enriched Langerhans cells express more HLA-DR determinants than blood-derived adherent cells (monocytes and dendritic cells)

When used as antigen-presenting cells, enriched Langerhans cells (LC) are known to induce a stronger proliferative T-cell response towards antigens than blood-derived adherent cells (a mixture of monocytes and dendritic cells). To study the mechanism behind this difference in accessory cell function, we have compared the quantitative expression of HLA-DR molecules on LC and adherent cells (AdC), using a radioimmunoassay system. The amount of HLA-DR determinants was calculated to be 50-100 times higher on LC than on AdC.