Origin of Langerhans cells in normal skin and chronic GVHD after hematopoietic stem-cell transplantation

STR typing of skin swabs from individuals after an allogeneic hematopoietic stem cell transplantation

One of the pre-requisites for forensic DNA analysis is the fact that all nucleated cells of a person carry the same genetic information. However, this is not the case for individuals who have received an allogeneic hematopoietic stem cell or bone marrow transplantation, as all new cells formed by the bone marrow no longer show the genetic information of the recipient but that of the donor, while all other cells still carry the original information before transplantation. Thus, STR typing of a blood sample after successful transplantation yields a DNA profile that differs from the recipient's original profile and corresponds to the donor genotype instead. Evidence from a routine case suggests that transplanted individuals may show donor alleles in skin swabs, as well. In order to examine this issue more closely, various skin swabs from 28 patients who have received an allogeneic hematopoietic stem cell transplantation were examined in this study. Swabs from the right and left palm, the back of the hand, one of the two upper arms, and the neck were collected from each person. Ninety-one of the 140 resulting swabs delivered useful results. All of those samples showed mixtures of recipient and donor DNA with different mixture ratios and the proportions of donor and recipient alleles revealed inter- and intra-individual differences. Those results were discussed with respect to graft versus host disease.

Langerhans cell origin and regulation

PURPOSE OF REVIEW

This article summarizes recent research on the ontogeny of Langerhans cells and regulation of their homeostasis in quiescent and inflamed conditions.

RECENT FINDINGS

Langerhans cells originate prenatally and may endure throughout life, independently of bone marrow-derived precursors. Fate-mapping experiments have recently resolved the relative contribution of primitive yolk sac and fetal liver hematopoiesis to the initial formation of Langerhans cells. In postnatal life, local self-renewal restores Langerhans cell numbers following chronic or low-grade inflammatory insults. However, severe inflammation recruits de-novo bone marrow-derived precursors in two waves; a transient population of classical monocytes followed by uncharacterized myeloid precursors that form a stable self-renewing Langerhans cell network as inflammation subsides. Human CD1c⁺ dendritic cells have Langerhans cell potential in vitro, raising the possibility that dendritic cell progenitors provide the second wave. Langerhans cell development depends upon transforming growth factor beta receptor signaling with distinct pathways active during differentiation and homeostasis. Langerhans cell survival is mediated by multiple pathways including mechanistic target of rapamycin and extracellular signal-regulated kinase signaling, mechanisms that become highly relevant in Langerhans cell neoplasia.

SUMMARY

The study of Langerhans cells continues to provide novel and unexpected insights into the origin and regulation of myeloid cell populations. The melding of macrophage and dendritic cell biology, shaped by a unique habitat, is a special feature of Langerhans cells.

Clinical and morphological diagnostics of skin manifestations in case of graft-versus-host disease

The graft-versus-host disease is a life-threatening complication of allogeneic bone marrow transplantation, which demands fast and reliable diagnostics. Goal. To study clinical features of the graft-versus-host disease as well as differential and diagnostic value of histological and immunohistochemical signs in skin biopsy samples in case of graft-versus-host disease (GvHD). Materials and methods. The authors made a comparative assessment of clinical data available for patients suffering from acute GvHD (50 patients) and toxic dermatitis (10 patients). Skin biopsy samples taken from patients from both groups underwent postmortem and immunohistochemistry examinations: the drugs were stained with hematoxylin and eosin as well as by using anti-CD3, CD20, CD4, CD8, FOXP3, CD56, CD1a and CD 68 antibodies. Results. Based on the results of clinical data assessments, no significant differences in the groups were revealed. The morphological examination revealed that the number of eosinophils, CD8+, CD1a+, CD3+ and FOXP3+ cells and share of FOXP3+ cells among Т lymphocytes was higher in the group with toxic dermatitis. Conclusion. An integrated assessment of clinical data and morphological examination results accompanied by the analysis of the population composition of the infiltrate is needed to diagnose the acute GvHD.

A question of persistence: Langerhans cells and graft-versus-host disease

Langerhans cells (LCs) have been scrutinized many times in studies of the pathogenesis of graft-versus-host disease (GVHD). As migratory dendritic cells, LCs are capable of direct antigen presentation to cytotoxic T cells. Their self-renewal capacity has led to speculation that persistent recipient LCs could provide a continuous source of host antigen to donor T cells infused during hematopoietic stem cell transplantation (HSCT). In this issue of Experimental Dermatology, a new study examines at the relationship between recipient LCs and chronic GVHD.

Dendritic Cell Therapy in an Allogeneic-Hematopoietic Cell Transplantation Setting: An Effective Strategy toward Better Disease Control?

Hematopoietic cell transplantation (HCT) is a last treatment resort and only potentially curative treatment option for several hematological malignancies resistant to chemotherapy. The induction of profound immune regulation after allogeneic HCT is imperative to prevent graft-versus-host reactions and, at the same time, allow protective immune responses against pathogens and against tumor cells. Dendritic cells (DCs) are highly specialized antigen-presenting cells that are essential in regulating this balance and are of major interest as a tool to modulate immune responses in the complex and challenging phase of immune reconstitution early after allo-HCT. This review focuses on the use of DC vaccination to prevent cancer relapses early after allo-HCT. It describes the role of host and donor-DCs, various vaccination strategies, different DC subsets, antigen loading, DC maturation/activation, and injection sites and dose. At last, clinical trials using DC vaccination post-allo-HCT and the future perspectives of DC vaccination in combination with other cancer immunotherapies are discussed.