Phenotypic and Functional Properties of Human Steady State CD14+ and CD1a+ Antigen Presenting Cells and Epidermal Langerhans Cells

Cutaneous antigen presenting cells (APCs) are critical for the induction and regulation of skin immune responses. The human skin contains phenotypically and functionally distinct APCs subsets that are present at two separated locations. While CD1a^high LCs form a dense network in the epidermis, the CD14⁺ and CD1a⁺ APCs reside in the dermal compartment. A better understanding of the biology of human skin APC subsets is necessary for the improvement of vaccine strategies that use the skin as administration route. In particular, progress in the characterization of uptake and activatory receptors will certainly improve APC-targeting strategies in vaccination. Here we performed a detailed analysis of the expression and function of glycan-binding and pattern-recognition receptors in skin APC subsets. The results demonstrate that under steady state conditions human CD1a⁺ dermal dendritic cells (DCs) were phenotypically most mature as measured by the expression of CD83 and CD86, whereas the CD14⁺ cells showed a higher expression of the CLRs DC-SIGN, mannose receptor and DCIR and had potent antigen uptake capacity. Furthermore, steady state LCs showed superior antigen cross-presentation as compared to the dermal APC subsets. Our results also demonstrate that the TLR3 ligand polyribosinic-polyribocytidylic acid (pI:C) was the most potent stimulator of cytokine production by both LCs and dDCs. These studies warrant further exploration of human CD1a⁺ dDCs and LCs as target cells for cancer vaccination to induce anti-tumor immune responses.     

Human Langerhans Cells Control Th Cells via Programmed Death-Ligand 1 in Response to Bacterial Stimuli and Nickel-Induced Contact Allergy

Langerhans cells (LCs) are suspected to initiate inflammatory immune responses to contact allergens and pathogenic bacteria. In chronic infectious diseases, programmed death ligand (PD-L) 1 exhibits both inhibitory and costimulatory functions on T cell-mediated activation and tolerance. Here, we investigated the effects of contact allergens and bacterial stimuli on PD-L1 expression in LCs and the effects of altered PD-L1 expression on cytokine release of subsequently cocultured T cells. Monocyte-derived LCs (MoLCs), LCs, and skin sections of patients suffering from allergic contact dermatitis were challenged with nickel and then analyzed for PD-L1 expression by confocal laser scanning microscopy and flow cytometry. In blocking experiments, we found that the release of Th cell specific cytokines was dependent on both stimulation of LCs and inhibition of PD-L1-PD-1 interactions. Stimulation with peptidoglycan (PGN) or lipopolysaccharide (LPS) and blockage of PD-L1 with a specific antibody triggered the release of high levels of IL-17, IL-22, TNF-α, and IFN-γ in CD4⁺T cells. If nickel was used as a stimulus, blockage of PD-L1 led to high amounts of TNF-α and IL-22. A closer look revealed PD-L1-dependent upregulation of IL-17 secretion in FACS-sorted CCR6⁺/CCR4⁺ T memory cells. In the presence of anti-PD-L1, PGN induced secretion of IFN-γ and IL-17 in total CCR6⁺ cells, while nickel triggered secretion of IFN-γ and IL-17 exclusively in CCR6⁺/CCR4⁺ cells. Our findings suggest that PD-L1 on LCs plays a crucial role in type IV allergic reactions and in response to bacterial stimuli by controlling the nature of inflammatory Th cell responses.     

Differential Capacity of Human Skin Dendritic Cells to Polarize CD4+T Cells into IL-17, IL-21 and IL-22 Producing Cells

Accumulating evidence suggests a contribution of T cell-derived IL-17, IL-21 and IL-22 cytokines in skin immune homeostasis as well as inflammatory disorders. Here, we analyzed whether the cytokine-producing T lymphocytes could be induced by the different subsets of human skin dendritic cells (DCs), i.e., epidermal Langerhans cells (LCs), dermal CD1c⁺CD14⁻ and CD14⁺ DCs (DDCs). DCs were purified following a 2-day migration from separated epidermal and dermal sheets and co-cultured with allogeneic T cells before cytokine secretion was explored. Results showed that no skin DCs could induce substantial IL-17 production by naïve CD4⁺ or CD8⁺T lymphocytes whereas all of them could induce IL-17 production by memory T cells. In contrast, LCs and CD1c⁺CD14⁻DDCs were able to differentiate naïve CD4⁺T lymphocytes into IL-22 and IL-21-secreting cells, LCs being the most efficient in this process. Intracellular cytokine staining showed that the majority of IL-21 or IL-22 secreting CD4⁺T lymphocytes did not co-synthesized IFN-γ, IL-4 or IL-17. IL-21 and IL-22 production were dependent on the B7/CD28 co-stimulatory pathway and ICOS-L expression on skin LCs significantly reduced IL-21 level. Finally, we found that TGF-β strongly down-regulates both IL-21 and IL-22 secretion by allogeneic CD4⁺ T cells. These results add new knowledge on the functional specialization of human skin DCs and might suggest new targets in the treatment of inflammatory skin disorders.     

Relay of Herpes Simplex Virus between Langerhans Cells and Dermal Dendritic Cells in Human Skin

The mechanism by which immunity to Herpes Simplex Virus (HSV) is initiated is not completely defined. HSV initially infects mucosal epidermis prior to entering nerve endings. In mice, epidermal Langerhans cells (LCs) are the first dendritic cells (DCs) to encounter HSV, but it is CD103⁺ dermal DCs that carry viral antigen to lymph nodes for antigen presentation, suggesting DC cross-talk in skin. In this study, we compared topically HSV-1 infected human foreskin explants with biopsies of initial human genital herpes lesions to show LCs are initially infected then emigrate into the dermis. Here, LCs bearing markers of maturation and apoptosis formed large cell clusters with BDCA3⁺ dermal DCs (thought to be equivalent to murine CD103⁺ dermal DCs) and DC-SIGN⁺ DCs/macrophages. HSV-expressing LC fragments were observed inside the dermal DCs/macrophages and the BDCA3⁺ dermal DCs had up-regulated a damaged cell uptake receptor CLEC9A. No other infected epidermal cells interacted with dermal DCs. Correspondingly, LCs isolated from human skin and infected with HSV-1 in vitro also underwent apoptosis and were taken up by similarly isolated BDCA3⁺ dermal DCs and DC-SIGN⁺ cells. Thus, we conclude a viral antigen relay takes place where HSV infected LCs undergo apoptosis and are taken up by dermal DCs for subsequent antigen presentation. This provides a rationale for targeting these cells with mucosal or perhaps intradermal HSV immunization.     

Dendritic Cells Cause Bone Lesions in a New Mouse Model of Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease caused by the clonal accumulation of dendritic Langerhans cells, which is often accompanied by osteolytic lesions. It has been reported that osteoclast-like cells play a major role in the pathogenic bone destruction seen in patients with LCH and these cells are postulated to originate from the fusion of DCs. However, due to the lack of reliable animal models the pathogenesis of LCH is still poorly understood. In this study, we have established a mouse model of histiocytosis- recapitulating human disease for osteolytic lesions seen in LCH patients. At 12 weeks after birth, severe bone lesions were observed in our multisystem histiocytosis (Mushi) model, when CD8α conventional dendritic cells (DCs) are transformed (MuTuDC) and accumulate. Most importantly, our study demonstrates that bone loss in LCH can be accounted for the transdifferentiation of MuTuDCs into functional osteoclasts both in vivo and in vitro. Moreover, we have shown that injected MuTuDCs reverse the osteopetrotic phenotype of oc/oc mice in vivo. In conclusion, our results support a crucial role of DCs in bone lesions in histiocytosis patients. Furthermore, our new model of LCH based on adoptive transfer of MuTuDC lines, leading to bone lesions within 1–2 weeks, will be an important tool for investigating the pathophysiology of this disease and ultimately for evaluating the potential of anti-resorptive drugs for the treatment of bone lesions.     

Selective Susceptibility of Human Skin Antigen Presenting Cells to Productive Dengue Virus Infection

Dengue is a growing global concern with 390 million people infected each year. Dengue virus (DENV) is transmitted by mosquitoes, thus host cells in the skin are the first point of contact with the virus. Human skin contains several populations of antigen-presenting cells which could drive the immune response to DENV in vivo: epidermal Langerhans cells (LCs), three populations of dermal dendritic cells (DCs), and macrophages. Using samples of normal human skin we detected productive infection of CD14⁺ and CD1c⁺ DCs, LCs and dermal macrophages, which was independent of DC-SIGN expression. LCs produced the highest viral titers and were less sensitive to IFN-β. Nanostring gene expression data showed significant up-regulation of IFN-β, STAT-1 and CCL5 upon viral exposure in susceptible DC populations. In mice infected intra-dermally with DENV we detected parallel populations of infected DCs originating from the dermis and migrating to the skin-draining lymph nodes. Therefore dermal DCs may simultaneously facilitate systemic spread of DENV and initiate the adaptive anti-viral immune response.     

Inflammation in disseminated lesions: an analysis of CD4+, CD20+, CD68+, CD31+ and vW+ cells in non-ulcerated lesions of disseminated leishmaniasis

Disseminated leishmaniasis (DL) differs from other clinical forms of the disease due to the presence of many non-ulcerated lesions (papules and nodules) in non-contiguous areas of the body. We describe the histopathology of DL non-ulcerated lesions and the presence of CD4-, CD20-, CD68-, CD31- and von Willebrand factor (vW)-positive cells in the inflamed area. We analysed eighteen biopsies from non-ulcerated lesions and quantified the inflamed areas and the expression of CD4, CD20, CD68, CD31 and vW using Image-Pro software (Media Cybernetics). Diffuse lymphoplasmacytic perivascular infiltrates were found in dermal skin. Inflammation was observed in 3-73% of the total biopsy area and showed a significant linear correlation with the number of vW⁺ vessels. The most common cells were CD68⁺ macrophages, CD20⁺ B-cells and CD4⁺ T-cells. A significant linear correlation between CD4⁺ and CD20⁺ cells and the size of the inflamed area was also found. Our findings show chronic inflammation in all DL non-ulcerated lesions predominantly formed by macrophages, plasmacytes and T and B-cells. As the inflamed area expanded, the number of granulomas and extent of the vascular framework increased. Thus, we demonstrate that vessels may have an important role in the clinical evolution of DL lesions.     

Systemic Inflammation in Progressive Multiple Sclerosis Involves Follicular T-Helper,Th17- and Activated B-Cells and Correlates with Progression

Pathology studies of progressive multiple sclerosis (MS) indicate a major role of inflammation including Th17-cells and meningeal inflammation with ectopic lymphoid follicles, B-cells and plasma cells, the latter indicating a possible role of the newly identified subset of follicular T-helper (T_FH) cells. Although previous studies reported increased systemic inflammation in progressive MS it remains unclear whether systemic inflammation contributes to disease progression and intrathecal inflammation. This study aimed to investigate systemic inflammation in progressive MS and its relationship with disease progression, using flow cytometry and gene expression analysis of CD4⁺ and CD8⁺T-cells, B-cells, monocytes and dendritic cells. Furthermore, gene expression of cerebrospinal fluid cells was studied. Flow cytometry studies revealed increased frequencies of ICOS⁺T_FH-cells in peripheral blood from relapsing-remitting (RRMS) and secondary progressive (SPMS) MS patients. All MS subtypes had decreased frequencies of Th1 T_FH-cells, while primary progressive (PPMS) MS patients had increased frequency of Th17 T_FH-cells. The Th17-subset, interleukin-23-receptor⁺CD4⁺T-cells, was significantly increased in PPMS and SPMS. In the analysis of B-cells, we found a significant increase of plasmablasts and DC-SIGN⁺ and CD83⁺B-cells in SPMS. ICOS⁺T_FH-cells and DC-SIGN⁺B-cells correlated with disease progression in SPMS patients. Gene expression analysis of peripheral blood cell subsets substantiated the flow cytometry findings by demonstrating increased expression of IL21, IL21R and ICOS in CD4⁺T-cells in progressive MS. Cerebrospinal fluid cells from RRMS and progressive MS (pooled SPMS and PPMS patients) had increased expression of T_FH-cell and plasmablast markers. In conclusion, this study is the first to demonstrate the potential involvement of activated T_FH-cells in MS. The increased frequencies of Th17-cells, activated T_FH- and B-cells parallel findings from pathology studies which, along with the correlation between activated T_FH- and B-cells and disease progression, suggest a pathogenic role of systemic inflammation in progressive MS. These observations may have implications for the treatment of progressive MS.     

Comparative Immune Phenotypic Analysis of Cutaneous Squamous Cell Carcinoma and Intraepidermal Carcinoma in Immune-Competent Individuals: Proportional Representation of CD8+ T-Cells but Not FoxP3+ Regulatory T-Cells Is Associated with Disease Stage

Squamous Cell Carcinoma (SCC) is a type of non-melanoma skin cancer prevalent in immune-suppressed transplant recipients and older individuals with a history of chronic sun-exposure. SCC itself is believed to be a late-stage manifestation that can develop from premalignant lesions including Intraepidermal Carcinoma (IEC). Notably, while SCC regression is rare, IEC typically regresses in response to immune modifying topical treatments, however the underlying immunological reasons for these differential responses remain unclear. This study aimed to define whether IEC and SCC are associated with distinct immune profiles. We investigated the immune cell infiltrate of photo-damaged skin, IEC, and SCC tissue using 10-colour flow cytometry following fresh lesion digest. We found that IEC lesions contain higher percentages of CD3⁺ T-cells than photo-damaged skin, however, the abundance of CD3⁻CD56⁺ Natural Killer (NK) cells, CD11c⁺HLA-DR⁺ conventional Dendritic Cells (cDC), BDCA-2⁺HLA-DR⁺ plasmacytoid DC (pDC), FoxP3⁺ Regulatory T-cells (T-reg), Vα24⁺Vβ11⁺ invariant NKT-cells, and γδ Tcells did not alter with disease stage. Within the total T-cell population, high percentages of CD4⁺ T-cells were associated with SCC, yet CD8⁺ T-cells were less abundant in SCC compared with IEC. Our study demonstrates that while IEC lesions contain a higher proportion of T-cells than SCC lesions in general, SCC lesions specifically display a lower abundance of CD8⁺ T-cells than IEC. We propose that differences in CD8⁺ T-cell abundance contribute critically to the different capacity of SCC and IEC to regress in response to immune modifying topical treatments. Our study also suggests that a high ratio of CD4⁺ T-cells to CD8⁺ T-cells may be a immunological diagnostic indicator of late-stage SCC development in immune-competent patients.     

Decreased Langerhans Cell Responses to IL-36γ: Altered Innate Immunity in Patients with Recurrent Respiratory Papillomatosis

Recurrent respiratory papillomatosis (RRP) is a rare, chronic disease caused by human papillomaviruses (HPVs) types 6 and 11 that is characterized by the polarization of adaptive immune responses that support persistent HPV infection. Respiratory papillomas express elevated mRNA levels of IL-36γ, a proinflammatory cytokine in comparison to autologous clinically normal laryngeal tissues; however there is no evidence of inflammation in these lesions. Consistent with this, respiratory papillomas do not contain T_H1-like CD4⁺ T-cells or cytotoxic CD8⁺ T-cells, but instead contain a predominance of T_H2-like and T regulatory cells (Tregs). In addition, papillomas also are infiltrated with immature Langerhans cells (iLCs). In this study, we show that papilloma cells express IL-36γ protein, and that human keratinocytes transduced with HPV11 have reduced IL-36γ secretion. We now provide the first evidence that peripheral blood-derived iLCs respond to IL-36γ by expressing inflammatory cytokines and chemokines. When stimulated with IL-36γ, iLCs from patients with RRP had lower expression levels of the T_H2-like chemokine CCL-20 as compared with controls. Patients’ iLCs also had decreased steady state levels of CCL-1, which is a proinflammatory chemokine. Moreover, CCL-1 levels in iLCs inversely correlated with the severity of RRP. The combined decrease of T_H1- and a T_H2-like chemokines by iLCs from patients could have consequences in the priming of IFN-γ expression by CD8⁺ T-cells. Taken together, our results suggest that, in RRP, there is a defect in the proinflammatory innate immune responses made by iLCs in response to IL-36γ. The consequence of this defect may lead to persistent HPV infection by failing to support an effective HPV-specific, T_H1-like and/or T_c1-like adaptive response, thus resulting in the predominant T_H2-like and/or Treg micromilieu present in papillomas.     

Experimental Human Pneumococcal Carriage Augments IL-17A-dependent T-cell Defence of the Lung

Pneumococcal carriage is both immunising and a pre-requisite for mucosal and systemic disease. Murine models of pneumococcal colonisation show that IL-17A-secreting CD4⁺ T-cells (Th-17 cells) are essential for clearance of pneumococci from the nasopharynx. Pneumococcal-responding IL-17A-secreting CD4⁺ T-cells have not been described in the adult human lung and it is unknown whether they can be elicited by carriage and protect the lung from pneumococcal infection. We investigated the direct effect of experimental human pneumococcal nasal carriage (EHPC) on the frequency and phenotype of cognate CD4⁺ T-cells in broncho-alveolar lavage and blood using multi-parameter flow cytometry. We then examined whether they could augment ex vivo alveolar macrophage killing of pneumococci using an in vitro assay. We showed that human pneumococcal carriage leads to a 17.4-fold (p = 0.007) and 8-fold (p = 0.003) increase in the frequency of cognate IL-17A⁺ CD4⁺ T-cells in BAL and blood, respectively. The phenotype with the largest proportion were TNF⁺/IL-17A⁺ co-producing CD4⁺ memory T-cells (p<0.01); IFNγ⁺ CD4⁺ memory T-cells were not significantly increased following carriage. Pneumococci could stimulate large amounts of IL-17A protein from BAL cells in the absence of carriage but in the presence of cognate CD4⁺ memory T-cells, IL-17A protein levels were increased by a further 50%. Further to this we then show that alveolar macrophages, which express IL-17A receptors A and C, showed enhanced killing of opsonised pneumococci when stimulated with rhIL-17A (p = 0.013). Killing negatively correlated with RC (r = −0.9, p = 0.017) but not RA expression. We conclude that human pneumococcal carriage can increase the proportion of lung IL-17A-secreting CD4⁺ memory T-cells that may enhance innate cellular immunity against pathogenic challenge. These pathways may be utilised to enhance vaccine efficacy to protect the lung against pneumonia.     

TRP expression pattern and the functional importance of TRPC3 in primary human T-cells

TRP proteins form ion channels which are activated following receptor stimulation. In T-cell lines, expression data of TRP proteins have been published. However, almost no data about TRP expression is available in primary human T-cells. Using RT-PCR and quantitative RT-PCR, we compare the expression of TRP mRNA in 1) human peripheral blood lymphocytes, which are a mix of mostly mono-nuclear blood lymphocytes but contain other leucocytes, 2) a pure human CD4⁺ T-helper cell population in the resting (= naïve) and activated (= effector) state, and 3) two commonly used CD4⁺ Jurkat T-cell lines, E6-1 and parental. To mimic physiological cell stimulation, we analyzed TRP expression in primary human cells in a quantitative way over several days following formation of an immunological synapse through stimulation with antibody-coated beads. The TRP expression profile of primary human T-cells was significantly different from Jurkat T-cells. Among the TRP mRNAs of the TRPC, TRPM, and TRPV family, we found consistent expression of TRPC1, TRPC3, TRPV1, TRPM2, and TRPM7 in primary human CD4⁺ T-cells of all analyzed blood donors. Among these, TRPC3 and TRPM2 were strongly up-regulated following stimulation, but with different kinetics. We found that TRPC3 modulates Ca²⁺-dependent proliferation of primary CD4⁺ T-cells indicating that TRPC3 may be involved in Ca²⁺ homeostasis in T-cells besides the well-established STIM and ORAI proteins which are responsible for store-operated Ca²⁺ entry.     

Induced Expression of FcγRIIIa (CD16a) on CD4+ T Cells Triggers Generation of IFN-γhigh Subset

Whether or not CD4⁺ T-cells express low affinity receptor FcγRIIIa (CD16a) in disease pathology has not been examined in great detail. In this study, we show that a subset of activated CD4⁺ T-cells in humans express FcγRIIIa. The ligation of FcγRIIIa by immune complexes (ICs) in human CD4⁺ T-cells produced co-stimulatory signal like CD28 that triggered IFN-γ production. The induced expression of FcγRIIIa on CD4⁺ helper T-cells is an important finding since these receptors via ITAM contribute to intracellular signaling. The induced expression of FcγRIIIa on CD4⁺ T helper cells and their ability to co-stimulate T-cell activation are important and novel findings that may reveal new pathways to regulate adaptive immune responses during inflammation and in autoimmunity.     

Immunohistochemical detection of Langerhans cells in dental granulomas and radicular cysts

Objective Dental granulomas (DGs) and radicular cysts (RCs) are chronic periapical lesions frequently involving the jaws. Langerhans cells (LCs) are dendritic cells responsible for the presentation of antigens to T lymphocytes. This study examined the expression of LCs in DG and RCs by immunohistochemical staining. Study Design Eighteen cases of DGs and 26 cases of RCs were analyzed using anti-CD1a marker. Results CD1a-labeled LCs were observed in 11.1% of DGs and in 69.2% of RCs, showing a significant correlation (P < 0.0001; Fisher’s test). In DGs, LCs were only observed in granulation tissue, showing discrete immunostaining density. In RCs, LCs exhibited both a round and a dendritic shape in all epithelial layers. Although a correlation was observed between immunostaining density and epithelial thickness, as well as between immunostaining and inflammatory intensity, the differences were not significant in radicular cysts. Conclusion Langerhans cells provide important insight into the immunopathogenesis of chronic periapical lesions.     

Differential expression of co-signal molecules and migratory properties in four distinct subsets of migratory dendritic cells from the oral mucosa

Variations in co-signal ligand expression and cytokine production greatly influence the antigen-presenting properties of migrating DCs in regional lymph nodes (RLNs). Here we investigated DCs migrating from the oral mucosa using CD326 and CD103 antigens for discriminate CD207⁺ Langerhans cells (LCs) from CD207⁺ submucosal DCs (SMDCs). Similar to DCs migrating from the skin, we identified four distinct oral mucosal DC (OMDC) subsets, CD11c^hiCD207⁻CD103⁻CD326^intCD11b^hi (F1; resident CD11b^hi SMDCs), CD11c^int/loCD207^-CD103^-CD326^loCD11b^int/hi (F2; newly recruited blood-derived SMDCs), CD11c^int/loCD207⁺CD103⁺CD326^int/hiCD11b^lo (CD103⁺ F3; resident CD207⁺ SMDCs), and CD11c^int/loCD207⁺CD103^-CD326^int/hiCD11b^lo (CD103^- F3; resident LCs). F1 DCs migrated rapidly after fluorescein isothiocyanate (FITC) painting and expressed notably high levels of CD86, CD273, and CD274 at an earlier time point. In contrast, CD103⁻ LCs expressing the highest levels of the epithelial cell adhesion molecule CD326 accounted for a minor subset at the earlier time point, but increased slowly with CD103⁺CD207⁺ SMDCs. However, their expression of CD86, CD273, and CD274 was very limited. The delayed migration and limited induction of co-signal ligands suggest that roles of OMLCs are distinct from those of the other three DC subsets. The identification of distinct subsets of OMDCs in RLNs may benefit efforts to determine the functional specialization of each subset in T cell responses against orally administrated antigens.     

CD34+ -derived Langerhans cell-like cells are different from epidermal Langerhans cells in their response to thymic stromal lymphopoietin

Thymic stromal lymphopoietin (TSLP) endows human blood‐derived CD11c⁺ dendritic cells (DCs) and Langerhans cells (LCs) obtained from human epidermis with the capacity to induce pro‐allergic T cells. In this study, we investigated the effect of TSLP on umbilical cord blood CD34⁺‐derived LC‐like cells. These cells are often used as model cells for LCs obtained from epidermis. Under the influence of TSLP, both cell types differed in several ways. As defined by CD83, CD80 and CD86, TSLP did not increase maturation of LC‐like cells when compared with freshly isolated LCs and epidermal émigrés. Differences were also found in the production of chemokine (C‐C motif) ligand (CCL)17. LCs made this chemokine only when primed by TSLP and further stimulated by CD40 ligation. In contrast, LC‐like cells released CCL17 in response to CD40 ligation, irrespective of a prior treatment with TSLP. Moreover, the CCL17 levels secreted by LC‐like cells were at least five times higher than those from migratory LCs. After maturation with a cytokine cocktail consisting of tumour necrosis factor‐α, interleukin (IL)‐1β, IL‐6 and prostaglandin (PG)E₂ LC‐like cells released IL‐12p70 in response to CD40 ligation. Most importantly and in contrast to LC, TSLP‐treated LC‐like cells did not induce a pro‐allergic cytokine pattern in helper T cells. Due to their different cytokine secretion and the different cytokine production they induce in naïve T cells, we conclude that one has to be cautious to take LC‐like cells as a paradigm for ‘real’ LCs from the epidermis.     

CD19 target-engineered T-cells accumulate at tumor lesions in human B-cell lymphoma xenograft mouse models

Adoptive T-cell therapy with CD19-specific chimeric antigen receptors (CARs) is promising for treatment of advanced B-cell malignancies. Tumor targeting of CAR-modified T-cells is likely to contribute therapeutic potency; therefore we examined the relationship between the ability of CD19-specific CAR (CD19-CAR)-transduced T-cells to accumulate at CD19⁺ tumor lesions, and their ability to provide anti-tumor effects in xenograft mouse models. Normal human peripheral blood lymphocytes, activated with immobilized RetroNectin and anti-CD3 antibodies, were transduced with retroviral vectors that encode CD19-CAR. Expanded CD19-CAR T-cells with a high transgene expression level of about 75% produced IL-2 and IFN-γ in response to CD19, and lysed both Raji and Daudi CD19⁺ human B-cell lymphoma cell lines. Furthermore, these cells efficiently accumulated at Raji tumor lesions where they suppressed tumor progression and prolonged survival in tumor-bearing Rag2^−/−γc^−/− immunodeficient mice compared to control cohorts. These results show that the ability of CD19-CAR T-cells to home in on tumor lesions is pivotal for their anti-tumor effects in our xenograft models, and therefore may enhance the efficacy of adoptive T-cell therapy for refractory B-cell lymphoma.     

Immune reconstitution in lymphoid tissue following potent antiretroviral therapy

During untreated HIV-1 infection, a chronic state of immune activation and inflammation develops at the lymphoid tissue sites of viral replication. The early effect of potent combination drug therapy is a reduction in peripheral viral burden and a reduction in the production of inflammatory and type 1 cytokines. Further along in treatment there are trends toward normalization in the frequencies of CD8⁸ T-cells, CD4⁺ CD45RA⁺ cells, as well as CD4⁺ CD45R0⁺ cells. Finally, the CD1a⁺ dendritic cell network is re-established and germinal centers are reformed. Although this restoration of the lymphoid dynamic form is coupled to a reconstitution of peripheral blood T-cell function in vitro and by skin testing, sterilizing immunity to HIV-1 does not develop. Furthermore there is no heightened development of cytotoxic CD8⁺ T-cell function at the site of HIV-1 latency. This is evidenced by a massive recrudescence of HIV-1 viral replication within lymphoid tissue when therapy is stopped. The development of supplemental therapies, which reconstitute anti-HIV-1 immunity, will be required. Specific defects in anti-HIV-1 activity which occur in lymphoid tissue during infection include a downregulation of perform expression by cytotoxic T-cells, the down regulation of the TCR signal transducing chain CD3ζ, and inadequate CD4⁺ T-cell help within the tissue compartment of immune regeneration.