The Cytokine TGF-ß Induces Interleukin-31 Expression from Dermal Dendritic Cells to Activate Sensory Neurons and Stimulate Wound Itching.

Cutaneous wound healing is associated with the unpleasant sensation of itching. Here we investigated the mechanisms underlying this type of itch, focusing on the contribution of soluble factors released during healing. We found high amounts of interleukin 31 (IL-31) in skin wound tissue during the peak of itch responses. Il31-/- mice lacked wound-induced itch responses. IL-31 was released by dermal conventional type 2 dendritic cells (cDC2s) recruited to wounds and increased itch sensory neuron sensitivity. Transfer of cDC2s isolated from late-stage wounds into healthy skin was sufficient to induce itching in a manner dependent on IL-31 expression. Addition of the cytokine TGF-ß1, which promotes wound healing, to dermal DCs in vitro was sufficient to induce Il31 expression, and Tgfbr1f/f CD11c-Cre mice exhibited reduced scratching and decreased Il31 expression in wounds in vivo. Thus, cDC2s promote itching during skin would healing via a TGF-ß-IL-31 axis with implications for treatment of wound itching.

Efficacy of Transplantation of Combination of Noncultured Dermal and Epidermal Cell Suspension vs Epidermal Cell Suspension Alone in Vitiligo: A Randomized Clinical Trial.

Importance: Surgical interventions, notably noncultured epidermal suspension (NCES), are the next line of treatment in patients with vitiligo who fail to respond to medical therapy. Noncultured epidermal suspension is usually performed in patients with vitiligo with duration of clinical stability (DS) of 12 months or longer because DS is a vital parameter in determining outcome of NCES. In this pilot study, we planned to assess the efficacy of a novel combination of noncultured epidermal cell suspension and noncultured dermal cell suspension (NCES and NDCS) in patients with vitiligo with shorter DS (3-6 months). Objective: To compare the efficacy of transplantation of NCES and NDCS vs NCES alone in patients with vitiligo with DS of 3 to 6 months. Design, Setting, and Participants: A single-center randomized clinical trial including 40 patients with focal, segmental, or generalized vitiligo with DS of 3 to 6 months or more than 12 months was carried out. Based on DS, 2 groups including 20 patients each were recruited (DS in group 1, 3 to 6 months; DS in group 2, more than 12 months). Each group was further randomized into 2 subgroups, A and B. Intervention: Patients in subgroups 1A and 2A underwent NCES alone, whereas patients in subgroups 1B and 2B underwent NCES and NDCS. Main Outcomes and Measures: Extent of repigmentation, color match, and pattern of repigmentation at 24 weeks. Results: Of the 40 study participants, mean (SD) age was 24.9 (4.0) years and 24 (60%) were women; in group 1 with DS for 3 to 6 months, more than 75% repigmentation at 24 weeks was observed in all 10 patients in subgroup 1B (NCES and NDCS) compared with 3 of 10 patients in subgroup 1A (NCES) (100% vs 30%, P = .003). In group 2 (DS > 12 months), the same was observed in 6 of 10 patients in subgroup 2A and 7 of 10 patients in subgroup 2B (NCES) (60% vs 70%, P > .99). The 2 groups and subgroups did not show any significant differences with respect to color matching and pattern of repigmentation. Conclusions and Relevance: Combination of NCES and NDCS resulted in excellent response in patients with vitiligo with shorter duration of clinical stability compared with NCES alone. This combination may be used early in the course of stable vitiligo without waiting for a period of 12 months or more since last clinical activity. Trial Registration: ClinicalTrials.gov identifier: NCT03013049.

[Current state of the problem of allotransplantation of Langerhans cells (achievements and prospects)]. / Sovremennoe sostoianie problemy allotransplantatsii kletok Langergansa (dostizheniia i perspektivy).

Literature data devoted to transplantation of Langerhans cells have been analyzed. The main stages, indications, dissection of islets, immunosuppressive therapy, complications and data of the latest clinical trials were discussed.

New routes of allergen immunotherapy.

OBJECTIVES: Allergen immunotherapy is the only cure for immunoglobulin E mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) are the most common treatments. In this article, we reviewed new routes of allergen immunotherapy. METHODS: Data on alternative routes to allow intralymphatic immunotherapy (ILIT), epicutaneous immunotherapy (EPIT), local nasal immunotherapy (LNIT), oral immunotherapy (OIT), and oral mucosal immunotherapy (OMIT) were gathered from the literature and were discussed. RESULTS: ILIT features direct injection of allergens into lymph nodes. ILIT may be clinically effective after only a few injections and induces allergen-specific immunoglobulin G, similarly to SCIT. A limitation of ILIT is that intralymphatic injections are required. EPIT features allergen administration by using patches mounted on the skin. EPIT seeks to target epidermal antigen-presenting Langerhans cells rather than mast cells or the vasculature; this should reduce both local and systemic adverse effects. LNIT involves the spraying of allergen extracts into the nasal cavity. Natural or chemically modified allergens (the latter, termed allergoids, lack immunoglobulin E reactivity) are prepared in a soluble form. OIT involves the regular administration of small amounts of a food allergen by mouth and commences with low oral doses, which are then increased as tolerance develops. OMIT seeks to deliver allergenic proteins to an expanded population of Langerhans cells in the mucosa of the oral cavity. CONCLUSIONS: ILIT, EPIT, LNIT, OIT, and OMIT are new routes for allergen immunotherapy. They are safe and effective.

Human epidermal Langerhans cells replenish skin xenografts and are depleted by alloreactive T cells in vivo.

Epidermal Langerhans cells (LC) are potent APCs surveying the skin. They are crucial regulators of T cell activation in the context of inflammatory skin disease and graft-versus-host disease (GVHD). In contrast to other dendritic cell subtypes, murine LC are able to reconstitute after local depletion without the need of peripheral blood-derived precursors. In this study, we introduce an experimental model of human skin grafted to NOD-SCID IL2Rγ(null) mice. In this model, we demonstrate that xenografting leads to the transient loss of LC from the human skin grafts. Despite the lack of a human hematopoietic system, human LC repopulated the xenografts 6 to 9 wk after transplantation. By staining of LC with the proliferation marker Ki67, we show that one third of the replenishing LC exhibit proliferative activity in vivo. We further used the skin xenograft as an in vivo model for human GVHD. HLA-disparate third-party T cells stimulated with skin donor-derived dendritic cells were injected intravenously into NOD-SCID IL2Rγ(null) mice that had been transplanted with human skin. The application of alloreactive T cells led to erythema and was associated with histological signs of GVHD limited to the transplanted human skin. The inflammation also led to the depletion of LC from the epidermis. In summary, we provide evidence that human LC are able to repopulate the skin independent of blood-derived precursor cells and that this at least partly relates to their proliferative capacity. Our data also propose xeno-transplantation of human skin as a model system for studying the role of skin dendritic cells in the efferent arm of GVHD.

Antigen processing and MHC-II presentation by dermal and tumor-infiltrating dendritic cells.

MHC-II presentation by dendritic cells (DC) is necessary both for initial priming of CD4 T cells and for induction of peripheral effector function. Although CD4 T cells can be critical for competent immunization-mediated cancer immunosurveillance, unmanipulated CD4 T cell responses to poorly immunogenic tumors result in either complete ignorance or tolerance induction, suggesting inadequate DC function. In this study, we investigated the phenotype, Ag uptake, and MHC-II presentation capacity of normal dermal DC and tumor-infiltrating DC (TIDC) in both lymphoid and peripheral sites. We found that murine tumors were extensively infiltrated by partially activated TIDC that closely resembled dermal DC by surface marker expression. However, in contrast to dermal DC, TIDC were inefficient at MHC-II presentation due to poor intrinsic protein uptake capability. This resulted in both inferior initiation of T cell responses in the draining lymph node and poor peripheral effector cell accumulation. In addition, TLR stimulation selectively enhanced MHC-II presentation of Ag by dermal DC, but not TIDC in the draining lymph node, and did not affect overall peripheral Ag uptake of either. These results show that TIDC are functionally distinct from normal interstitial DC, thus indicating that neoplastic tissues can evade effector CD4 T cells through modification of DC competence.

Epidermal Langerhans cells promote skin allograft rejection in mice with NF-kappa B-impaired T cells.

T cells play a major role in the acute rejection of transplanted organs. Using mice transgenic for a T-cell-restricted NF-kappaB super-repressor (IkappaBalphaDeltaN-Tg mice), we have previously shown that T-cell-NF-kappaB is essential for the acute rejection of cardiac but not skin allografts. In this study, we investigated the mechanism by which skin grafts activate IkappaBalphaDeltaN-Tg T cells. Rejection was not due to residual T-cell-NF-kappaB activity as mice with p50/p52(-/-) T cells successfully rejected skin grafts. Rather, skin but not cardiac allografts effectively induced proliferation of graft-specific IkappaBalphaDeltaN-Tg T cells. Rejection of skin grafts by IkappaBalphaDeltaN-Tg mice was in part dependent on the presence of donor Langerhans cells (LC), a type of epidermal dendritic cells (DC), as lack of LC in donor skin grafts resulted in prolongation of skin allograft survival and injection of LC at the time of cardiac transplantation was sufficient to promote cardiac allograft rejection by IkappaBalphaDeltaN-Tg mice. Our results suggest that LC allow NF-kappaB-impaired T cells to reach an activation threshold sufficient for transplant rejection. The combined blockade of T-cell-NF-kappaB with that of alternative pathways allowing activation of NF-kappaB-impaired T cells may be an effective strategy for tolerance induction to highly immunogenic organs.

Complete donor chimaerism of Langerhans cells in lymph node early after allogeneic bone marrow transplantation.

Host-derived Langerhans cells (LCs) are crucial antigen-presenting cells that cause graft-vs.-host disease after allogeneic haematopoietic stem cell transplantation (HSCT). However, chimaerism of LCs after allogeneic HSCT is largely unknown in humans. We here report a case that developed dermatopathic lymphadenitis accompanied by an accumulation of donor-derived LCs in the second month after allogeneic HSCT with reduced-intensity conditioning. This is the first case to show that donor LCs have the ability to migrate into draining lymph nodes and replace host LCs early after HSCT in humans.

Heart, but not skin, allografts from donors lacking Flt3 ligand exhibit markedly prolonged survival time.

Fms-like tyrosine kinase 3 ligand (Flt3L) administration leads to dramatic increases in dendritic cells (DC) in lymphoid and nonlymphoid tissues. Conversely, mice lacking Flt3L (Flt3L(-)/(-)) show severe reductions in both myeloid (CD11c(+)CD8alpha(-)) and lymphoid-related DC (CD11c(+)CD8alpha(+)) in the thymus and secondary lymphoid organs. In this study marked reductions in CD11c(+) interstitial cardiac DC and in dermal, but not epidermal, DC (Langerhans cells) were also observed. CD11c(+) cells that migrated from Flt3L(-/-) skin explants expressed lower surface MHC class II and costimulatory molecules and naive T cell allostimulatory activity than migratory wild-type (wt) C57BL/6 (B6) CD11c(+) cells. We examined the survival of Flt3L(-)/(-) heart or tail skin grafts (H2(b)) in allogeneic wt (BALB/c; H2(d)) recipients. The outcome of transplantation of BALB/c organs into Flt3L(-)/(-) recipients was also determined. Flt3L(-)/(-) mice rejected BALB/c heart or skin grafts with similar kinetics as B6 wt recipients. Trafficking of donor DC into host spleens or draining lymph nodes was markedly reduced after transplantation of Flt3L(-)/(-) heart, but not skin grafts, respectively. Compared with wt hearts, survival of Flt3L(-)/(-) hearts was markedly prolonged in BALB/c recipients (median survival time, 37 and 15 days, respectively; p < 0.001). Skin graft survival was unaffected. Rejection of Flt3L(-/-) hearts was precipitated by infusion of wt donor DC at the time of transplant. Thus, severe depletion of interstitial heart DC resulting from targeted gene disruption prolongs, but does not indefinitely extend, heart survival. Acute rejection of wt grafts in Flt3L(-/-) recipients reflects presumably an intact role of the direct pathway of allorecognition.

Langerhans cells beta 2-adrenoceptors: role in migration, cytokine production, Th priming and contact hypersensitivity.

We showed that norepinephrine (NE) hampers IL-12 and stimulates IL-10 production via adrenoceptors (ARs) in bone marrow-derived dendritic cells (BMDC) influencing their Th priming ability. Others have shown that Langerhans cells (LC) express mRNA for beta1-, beta2- and alpha1(A)-(ARs) and that catecholamines may inhibit the antigen-presenting capability via beta2-ARs. Here, we show that also BMDC express mRNA for beta1-, beta2-, alpha2(A)- and alpha2(C)-ARs. Inhibition of IL-12 is mediated by both beta2- and alpha2(A)-ARs, while stimulation of IL-10 by beta2-ARs only. In addition, LC migration, the contact hypersensitivity response (CHS) and production of IFN-gamma and IL-2 in draining lymph node cells is increased in mice treated topically with the beta2-AR antagonist ICI 118,551 during FITC sensitization. Activation of beta2-ARs in BMDC before adoptive transfer could reduce both migration and CHS response to FITC. Finally, preincubation of BMDC with LPS in presence of the specific beta2-AR agonist salbutamol impaired their chemotactic response to CCL19 and CCL21 and this effect was neutralized by anti-IL-10 mAb. We suggest that the physiological activation of beta2-ARs in DC (LC) results in stimulation of IL-10 which in turn restrains DC (LC) migration influencing antigen presentation and the consequent CHS response.

Granulocyte-macrophage colony-stimulating factor-based melanoma cell vaccines immunize syngeneic and allogeneic recipients via host dendritic cells.

Subcutaneous injection of GM-CSF-expressing cancer cells into experimental animals results in protective cancer immunity. To delineate the mode of action of such vaccines, we used trinitrophenyl, the antigenic moiety of the contact allergen trinitrochlorobenzene, as surrogate Ag. Trinitrophenyl-derivatized bone marrow-derived dendritic cells were found to elicit a contact hypersensitivity response in syngeneic, but not in allogeneic recipients, compatible with their expected mode of direct Ag presentation. When expressing GM-CSF, haptenized M3 melanoma cells were also able to induce a contact hypersensitivity response but, in contrast to bone marrow-derived dendritic cells, not only in syngeneic but also in allogeneic recipients. This argues for a critical role of host APC. To identify their nature, we introduced the beta-galactosidase (betagal) gene into M3-GM cells. Their administration activated betagal-specific, L(d)-restricted CTL in syngeneic BALB/c mice. Evaluation of lymph nodes draining M3-GM-betagal injection sites revealed the presence of cells presenting the respective L(d)-binding betagal peptide epitope. Based on their capacity to activate betagal-specific CTL, they were identified as being CD11c(+) dendritic cells. These experiments provide a rational basis for the use of GM-CSF-based melanoma cell vaccines in an allogeneic setting.

Drug-inducible, dendritic cell-based genetic immunization.

Determining the mechanism of Ag loading of Langerhans cells (LC) for genetic immunization (GI) is complicated by the inability to distinguish between the response generated by direct transfection of LC from that due to exogenous uptake. To unravel this mechanism, we examined the impact of gene gun treatment on LC with respect to their activation and migration from skin, transgene expression, and ability to initiate humoral and cellular immune responses upon transfer to naive mice. To assess responses generated by direct LC transfection, an RU486-inducible expression system was used as a GI vector. In vitro skin organ cultures were developed from gene gun immunized mouse ear specimens to obtain LC. Gene gun treatment markedly augmented (3-fold) LC migration from ear skin, and these LC expressed the transgene at RNA and protein levels. Transfer of 2 x 10(5) migratory cells resulted in identical cellular responses to, but 10-fold lower humoral responses than, standard GI. Using an RU486-inducible system, we were able to measure responses generated by directly transfected LC. Our results indicate that direct transfection is a predominant pathway for LC Ag loading. The ability to regulate transgene expression with inducible DC-based vaccines demonstrates a new level of immunological control.

Dendritic cell (DC)-based protection against an intracellular pathogen is dependent upon DC-derived IL-12 and can be induced by molecularly defined antigens.

Upon loading with microbial Ag and adoptive transfer, dendritic cells (DC) are able to induce immunity to infections. This offers encouragement for the development of DC-based vaccination strategies. However, the mechanisms underlying the adjuvant effect of DC are not fully understood, and there is a need to identify Ag with which to arm DC. In the present study, we analyzed the role of DC-derived IL-12 in the induction of resistance to Leishmania major, and we evaluated the protective efficacy of DC loaded with individual Leishmania Ag. Using Ag-pulsed Langerhans cells (LC) from IL-12-deficient or wild-type mice for immunization of susceptible animals, we showed that the inability to release IL-12 completely abrogated the capacity of LC to mediate protection against leishmaniasis. This suggests that the availability of donor LC-derived IL-12 is a requirement for the development of protective immunity. In addition, we tested the protective effect of LC loaded with Leishmania homolog of receptor for activated C kinase, gp63, promastigote surface Ag, kinetoplastid membrane protein-11, or Leishmania homolog of eukaryotic ribosomal elongation and initiation factor 4a. The results show that mice vaccinated with LC that had been pulsed with selected molecularly defined parasite proteins are capable of controlling infection with L. major. Moreover, the protective potential of DC pulsed with a given Leishmania Ag correlated with the level of their IL-12 expression. Analysis of the cytokine profile of mice after DC-based vaccination revealed that protection was associated with a shift toward a Th1-type response. Together, these findings emphasize the critical role of IL-12 produced by the sensitizing DC and suggest that the development of a DC-based subunit vaccine is feasible.

[The Langerhans cell: from in vitro production to use in cellular immunotherapy]. / La cellule de Langerhans: de la production in vitro à l'utilisation en immunothérapie cellulaire.

Dendritic cells constitute a family of antigen presenting cells defined by their morphology and their capacity to initiate primary immune response. Langerhans cells are paradigmatic dendritic cells, described in 1868 by a young medical student, Paul Langerhans in Berlin. Langerhans cells are present with epithelial cells in the epidermis, bronchi and mucosae. After antigenic challenge, Langerhans cells migrate into the T cell areas of proximal lymph nodes where they act as professional antigen-presenting cells. Langerhans cells originate in the bone marrow and CD34+ hematopoïetic progenitors are present in cord blood or circulating blood. They are actively involved in skin lesions of allergic contact dermatitis or atopic dermatitis, in cancer immunosurveillance and are infected by HIV in AIDS. Since 1992, Langerhans cells may be generated in vitro from CD34+ cord blood or circulating blood progenitors by culture with GM-CSF and TNF alpha, as well as from peripheral blood monocytes by culture with GM-CSF, IL4 and TGF beta 1. The possibility to obtain from the blood, the circulating progenitors of dendritic cells and the subsequent possibility to harvest a large number of these cells through in vitro culture using growth factors, have given rise to several very interesting therapeutic perspectives, especially in the field of anti-cancer immunotherapy. In dermatology advanced studies have concerned malignant melanomas. Anti-melanoma immunization trials were performed in patients, through dendritic cells charged with melanoma antigens. Side effects appear to be limited. Injections of antigenically charged dendritic cells were performed subcutaneously, intravenously or in the lymph nodes. Positive clinical responses were obtained with, in some cases, complete remission of the metastasis. These results open a particularly interesting perspective in the field of cancer treatment.

Differentiation of myeloid dendritic cells into CD8alpha-positive dendritic cells in vivo.

Bone marrow-derived dendritic cells (DC) represent a family of antigen-presenting cells (APC) with varying phenotypes. For example, in mice, CD8alpha(+) and CD8alpha(-) DC are thought to represent cells of lymphoid and myeloid origin, respectively. Langerhans cells (LC) of the epidermis are typical myeloid DC; they do not express CD8alpha, but they do express high levels of myeloid antigens such as CD11b and FcgammaR. By contrast, thymic DC, which derive from a lymphoid-related progenitor, express CD8alpha but only low levels of myeloid antigens. CD8alpha(+) DC are also found in the spleen and lymph nodes (LN), but the origin of these cells has not been determined. By activating and labeling CD8alpha(-) epidermal LC in vivo, it was found that these cells expressed CD8alpha on migration to the draining LN. Similarly, CD8alpha(-) LC generated in vitro from a CD8 wild-type mouse and injected into the skin of a CD8alphaKO mouse expressed CD8alpha when they reached the draining LN. The results also show that CD8alpha(+) LC are potent APC. After migration from skin, they localized in the T-cell areas of LN, secreted high levels of interleukin-12, interferon-gamma, and chemokine-attracting T cells, and they induced antigen-specific T-cell activation. These results demonstrate that myeloid DC in the periphery can express CD8alpha when they migrate to the draining LN. CD8alpha expression on these DC appears to reflect a state of activation, mobilization, or both, rather than lineage. (Blood. 2000;96:1865-1872)

[Management of diabetes induced by nearly total (95%) pancreatectomy with autologous transplantation of Langerhans cells]. / Majdnem totális (95%-os) pancreasresectiót követö pancreatogen diabetes kezelése Langerhans-sziget autotranszplantációval.

The present report concerns a patient who had undergone nearly total pancreatectomy (95%) with pancreatic islet autotransplantation for intractable pain caused by obstructive chronic pancreatitis. Islets were prepared by a modified collagenase digestion and were cultured in vitro in Eagel's medium in 5% CO2 in air at 37 degrees C for 5 days. The resultant preparation, containing about 150,000 islets, was injected into the recipient's liver via the umbilical vein. No complication occurred from the pancreatectomy or transplant. Postoperatively, the patient had complete relief of the abdominal pain, and the insulin-independent condition remained with normal fasting blood glucose, and hemoglobin A1c for 11 months. Subsequently the fasting hyperglycemia was evident, and the patient began oral antidiabetic medication, but 2 year after transplantation the insulin-dependent condition demanded exogenous insulin (24 U). At present the fasting serum C-peptide level is 0.6 ng/ml and the HbA1c of 5.8% confirms the normoglycemic condition at the same insulin dose. Islet auto-transplantation should be considered as an adjunct procedure to prevent or ameliorate diabetes after total or nearly total pancreatic resection.

In vitro production and transplantation of immunologically active skin equivalents.

In this study, we produced in vitro epidermal equivalents (EE) and skin equivalents (SE) with and without spleen lymphocytes. These skin substitutes were used for in vitro and in vivo (after isograft) histologic studies of cell and extracellular matrix organization and for protein synthesis. Then, using spleen lymphocytes in syngeneic and allogeneic SE, we assessed the immunogenicity of these skin substitutes after transplantation. In vitro histologic analyses showed that the epidermal organization of EE was comparable to that of SE. Fibroblasts and spleen lymphocytes were present in the extracellular matrix, as is the case in normal skin. Comparative immunohistologic studies after EE and SE isografting showed that the newly generated cutaneous tissues were well structured and vascularized. There were indications of physiologically active skin. The dermal component in these regenerated skins was, however, more organized after SE than after EE isografting, which indicates the importance of the dermis. Lastly, allografting of SE with and without spleen lymphocytes showed interesting results. Indeed, 10 days after allografting, all SE allowed skin regeneration comparable to isografts. Moreover, leukocyte infiltration in allografts was observed as early as 10 days and increased during the postgrafting period. Also, the presence of allogeneic spleen lymphocytes alone in syngeneic SE initiated recipient immune activation and induced leukocyte infiltration and graft rejection. The density of infiltrating leukocytes was higher in the complete allograft (allogeneic keratinocytes, fibroblasts, and spleen lymphocytes) compared with the partial allograft (only spleen lymphocytes were allogeneic), with the allograft (allogeneic keratinocytes and fibroblasts), and with the partial isograft (presence of syngeneic lymphocytes with allogeneic keratinocytes and fibroblasts). Mac-1+ and CD8+ cells were present in these leukocyte infiltrations, which indicates recipient immune system activation and allograft rejection. CD4-positive cells were not, however, seen in these leukocyte infiltrations. These results suggest that the incorporation of spleen lymphocytes in SE enhanced their immunogenicity as judged by leukocyte infiltration and the presence of CD8+ cells in the implants.

Dendritic cells of the oral mucosa and the induction of oral tolerance. A local affair.

The oral mucosa is an important site to induce immunological tolerance to protein antigens. Previously we have established that oral contacts to allergen can lead to systemic tolerance in both humans and experimental animals. Because of the importance of tolerance induction as a possible way to modulate allergic reactivity, we wished to study the mechanisms involved in efficient tolerance induction via the oral mucosa. Dendritic Langerhans' cells in both skin and oral epithelium are the first cells to encounter antigen. Therefore, possible functional differences between Langerhans' cells from skin and oral mucosa were studied by migration and transfer experiments. It was found that dendritic cells derived from the oral mucosa were not able to transfer tolerance, but that they acted as antigen-presenting cells in sensu stricto irrespective of the source and route of antigen administration.

The role of antigen-presenting cells in the regulation of delayed-type hypersensitivity. II. Epidermal Langerhans' cells and peritoneal exudate macrophages.

A new mechanism for regulation of delayed-type hypersensitivity (DTH) was investigated. The subcutaneous injection without adjuvant of syngeneic epidermal Langerhans' cells (LC) pulsed with keyhole limpet hemocyanin (KLH) into BALB/c mice gave rise to DTH upon challenge of the ear with the same antigen. When such cells were transferred intravenously, DTH did not occur, although the titer of anti-KLH antibodies was high. Peritoneal exudate macrophages (M phi) pulsed with KLH gave rise to neither DTH nor antibody production. The intravenous transfer of KLH-pulsed LC into mice immunized subcutaneously with KLH in complete Freund's adjuvant at the same time (in the sensitization phase) had a suppressive effect on DTH in an H-2-restricted way. M phi did not have immunoregulatory effects. When radiolabeled LC and M phi were transferred intravenously, they migrated into the spleen, but when they were transferred subcutaneously, they stayed in the skin or migrated into the lymph nodes. In splenectomized mice immunized with KLH, the intravenous transfer of LC pulsed with KLH neither caused the production of anti-KLH antibodies nor suppressed DTH. When Ia was expressed on the surface of M phi, the cells could present antigens, as LC could. These findings suggest that the anatomic sites at which an antigen is presented (i.e., spleen or draining lymph nodes) rather than the kind of cell that first presents an antigen to the immune system is important in deciding whether the immune response that takes place is DTH or antibody production.