Langerhans cells react with pan-leukocyte monoclonal antibody: ultrastructural documentation using a live cell suspension immunoperoxidase technique

Human Langerhans cells express a novel form of the leukocyte common antigen (CD45)

CD45 is a family of transmembrane glycoproteins that function as protein tyrosine phosphatases. All isoforms exhibit common CD45 epitopes, whereas the restricted CD45 epitopes (RA, RB, and RO) are each limited to one or more isoforms. In prior studies, we showed that human Langerhans cells in normal epidermis express a novel CD45 phenotype. They express common CD45 epitopes but are characteristically RA- RB- RO-. This suggests that Langerhans cells can express a novel form of CD45. In order to clarify this issue further, mRNA extracted from enriched Langerhans cell preparations was reverse transcribed into cDNA. The 5' portion of CD45 cDNA was then amplified using polymerase chain reaction primers complementary to exon 2 and exons 9-10, which flank the CD45 variable exon region (exons 4-6). Cloning and sequencing of the dominant 441 bp polymerase chain reaction product revealed the following exon configuration for the 5' translated region of Langerhans cells CD45: exon 3/7/8/9/10. This is the same exon configuration associated with the 180 kd CD45 isoform expressed by memory T cells and monocytes/macrophages; however, these cell types are RO+ whereas normal Langerhans cells are RO-. The RO epitope is known to be an oligosaccharide with a terminal sialic acid moiety. Therefore, we determined the expression of a related epitope, OPD4, by Langerhans cells. This is another terminal sialic acid moiety expressed by the 180 kd CD45 isoform of memory T cells but not by monocytes/macrophages. Langerhans cells were OPD4-. Our data suggest that memory T cells, monocytes/macrophages, and Langerhans cells all express a common CD45 transcript lacking exons 4-6; however, this transcript appears to undergo lineage-specific, post-translational glycosylation to create three distinct CD45 glycoproteins: RO+ OPD4+, RO+ OPD4-, and RO- OPD4-, which are expressed typically by memory T cells, monocytes/macrophages, and Langerhans cells, respectively. Because these epitopes are located extracellularly, they are postulated to allow differential responses to extracellular stimuli by creating differential ligand specificity.

Pretreatment of renal transplants with anti-CD45 antibodies: optimization of perfusion technique

Pig kidneys were perfused ex vivo with a monoclonal anti-pig CD45 antibody to determine optimum conditions for human kidney anti-CD45 perfusion, as such pretreatment may prolong renal allograft survival. Efficacy of perfused antibody uptake was assessed by immunohistochemical double-labelling of multiple renal biopsies. Antibody uptake by CD45+ cells was rapid, and maximal within one hour of perfusion. An antibody concentration of 40 micrograms/ml more effectively saturated available CD45 binding sites than lower concentrations. Whilst cortical perfusion was homogeneous (median uptake > 99%, minimum 90.0%) after 25, 50 or 100 ml perfusion with 40 micrograms/ml monoclonal antibody (mAb), the medulla was less evenly perfused with 25 ml (median uptake 82.6%) than with 50 or 100 ml (median uptake 98.5% and 98.7%, respectively). Prolongation of renal cold ischaemia of up to 46 hours prior to mAb perfusion did not adversely affect antibody binding. Clamping of the renal vein during and after mAb perfusion was associated with better cortical and medullary mAb uptake than if the vein was left unclamped. These data show that the vast majority of the kidney's CD45+ antigen-presenting cells can be bound by anti-CD45 mAb perfused ex vivo, if an adequate volume and concentration of mAb perfusate is employed and the renal vein is clamped during and after the process.

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.

Congenital self-healing Langerhans cell histiocytosis with persistent cellular immunological abnormalities

We describe an infant who presented at birth with numerous haemorrhagic and encrusted skin lesions, hepatomegaly, lymphadenopathy, raised hepatic transaminases, leucopenia and thrombocytopenia. The diagnosis of Langerhans cell histiocytosis was confirmed by immunohistochemistry, which demonstrated the presence of CD1, S-100 and DR positive cells in the skin infiltrate. The skin lesions resolved spontaneously after 6 weeks but recurred at 3 months and again were self involuting with resolution by 9 months. Persistent circulating T-cell abnormalities, including T-cell lymphopenia and the presence and persistence of peripheral blood CD1 + cells were noted throughout the first year of life.

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.

The widespread distribution of Langerhans cells in pathologic tissues: an ultrastructural and immunohistochemical study

Ultrastructural and/or immunohistochemical analysis of approximately 500 specimens revealed widespread distribution of Langerhans cells in pathologic specimens. More than half of the tissue specimens were from patients with a variety of pulmonary diseases. In all specimens in which Langerhans cells were identified ultrastructurally, they were also identified by an immunoperoxidase technique for the visualization of S-100 protein; the latter technique also revealed the dendritic nature of these cells. Langerhans cells were present in 80 to 93 per cent of 66 pulmonary adenocarcinomas and 17 per cent of squamous cell lung cancers; they were not observed in neuroendocrine lung carcinomas or mesotheliomas. They were also observed in benign inflammatory conditions of the lung of several types and in a variety of other malignant neoplasms and disease processes. The Langerhans cells in these tissues varied from few to many. They were most numerous in bronchioloalveolar cell carcinoma, sometimes appearing almost as frequently as tumor cells, and rare in some benign pulmonary conditions and other tumors. The function of Langerhans cells in these conditions is unknown, but they may have an immunologic function, such as antigen processing and presentation to T lymphocytes.

Leu-6-expressing cells in lymph nodes: dendritic cells phenotypically similar to interdigitating cells

Leu-6 is an antigen expressed by immature T cells, Langerhans cells, and indeterminate cells, the latter two of which are dendritic cells found predominantly within the skin. In dermatopathic lymphadenopathy, the paracortex is expanded by T cells and dendritic cells, including Langerhans cells. While the paracortex also contains Leu-6+ cells, the nature of such cells in lymph nodes has been controversial. To determine the characteristics of Leu-6+ paracortical cells, their morphologic, antigenic, and enzymatic features were studied in lymph nodes showing dermatopathic lymphadenopathy or reactive follicular hyperplasia. Immunologic studies with plastic, frozen, and paraffin sections demonstrated a dendritic cell morphology, a dendritic cell lineage phenotype (L3B12+, HLA-A,B,C+, HLA-DR+, S-100+), and the absence of T-cell lineage phenotype. These findings were corroborated by the enzymatic phenotype of these cells observed in plastic sections (membrane ATPase+, weak paranuclear acid phosphatase+, weak paranuclear alpha-napthylacetate esterase+). Although all paracortical dendritic cells were otherwise identical, only a subset of these cells were Leu-6+. The close phenotypic similarity between these Leu-6+ and Leu-6- paracortical dendritic cell subsets suggests a close ontogenetic relation. Furthermore, the greater abundance of the Leu-6+ subset in dermatopathic lymph nodes than in nodes exhibiting only reactive follicular hyperplasia, in conjunction with the presence of Leu-6+ dendritic cells within the sinuses of dermatopathic lymph nodes, suggests that at least some of the paracortical Leu-6+ cells are Leu-6+ Langerhans cells or indeterminate cells derived from the skin via the afferent lymphatics.

Depletion and repopulation of epidermal dendritic cells after allogeneic bone marrow transplantation in humans

We have observed marked depletion of epidermal dendritic cells, defined by monoclonal antibodies directed against HLA-DR (Ia-like) and T6 antigens, after allogeneic bone marrow transplantation. To more precisely characterize this observation, we examined a total of 39 sequential biopsies from 15 patients both before and after allogeneic bone marrow transplantation. Profound depletion of HLA-DR and T6-positive epidermal dendritic cells was observed early after transplantation (1-4 weeks), followed by gradual and variable repopulation. Transmission electron microscopy confirmed absence of dendritic cells in selected biopsies. Depletion of dendritic cells did not appear to be related to development of clinical or histologic evidence of graft-versus-host disease, suggesting that depletion may relate to pretransplant conditioning regimens. The rate of return of these cells, however, may be influenced by the presence or persistence of clinical disease. Repopulation of epidermal dendritic cells after initial depletion in bone marrow transplantation represents a human model relevant to studies concerned with the origin and kinetics of Langerhans cells.

Enrichment of murine and human Langerhans cells with solid phase immunoabsorption using pan-leukocyte monoclonal antibodies

Using a solid phase immunoabsorption (panning) technique, we have employed pan-leukocyte monoclonal antibodies to enrich and deplete murine and human Langerhans cells from cell suspensions of normal skin. Langerhans cell-enriched fractions contained 80-99% mononuclear cells, almost all of which had the ultrastructural features of Langerhans cells. These results are comparable to those achieved by panning for human Langerhans cells with anti-Leu-6(T6) antibody. Similarly, less than 1% of these cells were detectable in Langerhans cell-depleted fractions and such fractions were incapable of stimulating allogeneic lymphocytes in the skin cell-lymphocyte reaction. We conclude that panning with pan-leukocyte antibodies is an effective means of enriching or depleting Langerhans cells from heterogeneous skin cell suspensions and can yield results similar to those achieved with more Langerhans cell-specific reagents such as anti-Leu-6(T6). These findings are of particular significance to the enrichment and depletion of murine Langerhans cells since they express no known correlate of the human Leu-6(T6) antigen.