Fractionation of human bone-marrow mononuclear cells with peanut agglutinin: phenotypic characterization with monoclonal antibodies

Dynamic nature and function of epidermal Langerhans cells in vivo and in vitro: a review, with emphasis on human Langerhans cells

Epidermal Langerhans cells (LC) are Birbeck granule-containing bone-marrow-derived cells, which are located mainly in the suprabasal layer of the epidermis. They can be readily identified by their strong expression of CD1a and MHC class II molecules. In addition to these 'classical' properties, an extensive phenotypic profile of normal human LC, summarized in this review, is now available. The powerful capacity of LC to activate T lymphocytes is clearly documented and, to date, LC are recognized as the prominent antigen-presenting cells of the skin immune system. They are generally believed to pick up antigens encountered in the epidermis and to migrate subsequently from the epidermis to the skin-draining lymph nodes. Upon arrival in the paracortex of lymph nodes, the antigen-laden LC transform into interdigitating cells and they present antigen to naive T lymphocytes in a MHC class II-restricted fashion; this results in the generation of antigen-specific immune responses. It has also been demonstrated that transformation of LC into interdigitating cells occurs when LC are cultured in vitro. Both in vivo and in vitro studies have indicated that properties of LC, such as phenotype, morphology and the stimulatory potential to activate T lymphocytes, are dependent on the local microenvironment in which the LC reside. The essential role of LC in the induction of contact allergic skin reactions and skin transplant rejection is well established.

Human epidermal Langerhans cells express integrins of the beta 1 subfamily

The expression of VLA integrins on human epidermal Langerhans cells (LC) was investigated by indirect immunogold labeling on transmission electron microscopy, followed by a quantitative analysis. Labelings on suspensions enriched in freshly isolated LC were carried out with an antibody recognizing the beta 1 subunit, common to all members of the VLA family, and with antibodies specific for the six different alpha subunits, alpha 1 to alpha 6. Normal human epidermal LC were all beta 1 positive, of which 60% were highly positive. By labelings with different VLA-alpha-chain MoAb, there appeared two subpopulations of LC: one positive and one negative. On average 40% of LC bore small amounts of VLA-1 and VLA-3, 53% and 77% of LC expressed moderate amounts of VLA-2 and VLA-5, respectively, and VLA-4 and VLA-6 were expressed by 67% and 90% of LC, respectively. VLA proteins are mainly extracellular matrix protein receptors. VLA-6 (laminin receptor) and VLA-5 (fibronectin receptor) are expressed mainly by LC, and in this way could subserve LC to leave the epidermal compartment through the basement membrane, to migrate throughout the fibronectin network of the dermis before migrating via the afferent lymphatics to the regional lymph nodes, where they present antigen to T cells. VLA proteins such as VLA-4, VLA-3, or VLA-2, which are found involved in cell-cell contacts, could contribute to the promotion of T-cell activation by facilitating adherence between LC and T cells.

Phenotypic analysis of a large number of normal human bone marrow sample by flow cytometry

Bone marrow aspirates from 48 healthy donors (34 adults, 14 children) were analyzed by flow cytometry (FACS Analyzer) after purification of low-density bone marrow cells (Ld BMC) on a density gradient (d = 1,077) and labelling with 23 anti-hematopoietic cell monoclonal antibodies. Based on physical properties, these Ld BMC could be divided into four different populations called E, My, Mo and L, which comprised 14% +/- 9%, 31% +/- 16%, 10% +/- 5% and 45% +/- 14% of these cells, respectively. The phenotypic analysis of these different populations enabled the identification in E, of erythrocytes (Glycophorin A+, Rhesus D+, but negative for early erythroid differentiation markers such as the transferrin receptor (Tf. R) and the FA6-152 antigen); in My of cells of the myeloid lineage (VIM2+, HLA DR-); in Mo of cells of the monocytic lineage (VIM2+, CD14+) plus some myeloblasts (VIM2+, CD14-, HLADR+) and finally in L of a heterogeneous population including: 1. T lymphocytes labelled to the same extent by CD2, CD3, CD5 and CD6 (28% +/- 10%), B lymphocytes assessed by CD19 and CD20 (12% +/- 8%), Pre-B cells (CD10+ = 8% +/- 7%), less than 5% of "natural killer" cells (CD16+ or Leu7+) and finally, less than 6% of myelomonocytes (CD14+ and/or VIM2+). 2. The erythroid lineage (rhesus D+ = 42% +/- 20%, Tf.R+ and FA6-152+ = 32% +/- 12%). 3. Undifferentiated cells or progenitor cells (CD34+ = 7% +/- 5%). 4. Cells unlabelled by any antibodies (approximately 6%). We observed no difference between bone marrow samples from adults or children, with respect to physical properties, and with all but four immunological markers. A significantly higher proportion of B cells (CD19+ and CD10+) (P less than 0.001) and undifferentiated cells (CD34+ and HLADR+) (P less than 0.02) was observed in children. These data, obtained from a large number of bone marrow samples, could be used to quantify the imbalance of some bone marrow disorders.

Human normal-resting epidermal Langerhans cells do express the type 3 complement receptor

The expression of CR3 by murine-resting epidermal Langerhans cells (LC) is well established, but CR3 expression by human normal-resting epidermal LC has not yet been demonstrated. In this study, highly sensitive immunostaining techniques, such as immunogold labelling in transmission- and scanning-electron microscopy, were used on freshly isolated, LC-enriched, normal human epidermal cells. Human normal resting epidermal LC were found to be CR3+, since a low but significant number of gold granules labelled the plasma membrane of all the LC observed under transmission-electron microscopy, and all the epidermal cells showing LC morphology as observed by scanning-electron microscopy.

Langerhans cells of human mucosa

The ontogeny of human LC and their presence in all Malpighian epithelia underline their important role in immunoregulation of the skin and mucous membranes. LC are also found in buccal and esophageal mucosa, in cornea and conjunctiva, in pulmonary, vesical, vaginal and cervical epithelia as well as in placenta villi. In all these Malpighian epithelia, the presence of DR + LC is necessary and essential for the surveillance function against allergo-antigens and the emergence of neo-antigens associated with malignant transformations.

Bone marrow monocytes in histiocytosis X acquire some phenotypic features of Langerhans cells in long term bone marrow cultures

Bone marrow cells of a patient with Letterer-Siwe disease were cultured for three weeks in long-term bone marrow culture (LTBMC) conditions and examined at one-week intervals with a large panel of monoclonal antibodies by immunohistochemistry and by the immunogold transmission electron microscopy (immunoTEM) technique. Although at diagnosis the bone marrow showed a slight increase of monocytes with a normal phenotype, a rapid expansion of cells expressing CD1a and CD1c was observed already after 1 week of culture. A progressive increase in CD4, CD11b and CD11c expression was also observed. ImmunoTEM of cultured cells demonstrated that CD1a+ cells had macrophage-like morphology, and did not contain Birbeck granules. These findings indicate that bone marrow monocytes acquire some phenotypical features of Langerhans cells in LTBMC and support the hypothesis that these cells may derive directly from a bone marrow monocytic precursor.

T6 positive cells in the peripheral blood of burn patients: are they Langerhans cells precursors?

Peripheral blood mononuclear cells of 14 patients suffering thermal injury were separated by affinity chromatography on peanut agglutinin (PNA) coupled to Sepharose macrobeads. The resulting PNA positive subset was 14% of the total mononuclear population. About 30% of these cells were found to coexpress T6(CD1), Ia-like and the myeloid differentiation antigens My4(CDw14) and Mo1(CD11). In comparison, the PNA+ subset from normal blood donors (about 5% of total mononuclear cells) contained mature monocytes that were found to be T6 negative. Electron microscopic studies using immunogold labeling showed that the T6 positive cells were slightly smaller than monocytes but larger than the classical lymphocytes and had common morphologic features with the Langerhans cells of the skin. Considering that patients suffering extensive damage of the epidermis require fast renewal of all skin elements, it is possible that the cells we identified in their peripheral blood are the precursors of the Langerhans cells of the skin en route from bone marrow to the epidermis.