Eva Huter

Engagement of TLR2 Does not Reverse the Suppressor Function of Mouse Regulatory T Cells, but Promotes Their Survival

TLRs are a class of conserved pattern recognition receptors that are used by cells of the innate immune system. Recent studies have demonstrated the expression of TLRs on both human and mouse T cells raising the possibility that TLRs play a direct role in adaptive immunity. TLR2 is activated primarily by bacterial wall components including peptidoglycan and lipoproteins. Several studies have shown that mouse regulatory T (Treg) cells express TLR2 and claimed that engagement of TLR2 by synthetic ligands reversed their suppressive function. In contrary, enhancement of Treg function was observed following engagement of TLR2 on human Treg. We have reexamined the expression and function of TLR2 on mouse Treg purified from Foxp3-GFP knock-in mice. TLR2 ligation by TLR2 agonist, the synthetic bacterial lipoprotein Pam3CSK4, enhanced the proliferative responses of both conventional T cells and Treg in response to TLR stimulation in the absence of APC. Treatment of Foxp3+ Treg with Pam3CSK4 did not alter their suppressive function in vitro or in vivo and did not reduce their level of Foxp3 expression. An additional effect of TLR2 stimulation of Treg was induction of Bcl-xL resulting in enhanced survival in vitro. Treatment of mice with the TLR2 agonist enhanced the Ag-driven proliferation of Treg in vivo, but did not abolish their ability to suppress the development of experimental autoimmune encephalomyelitis. Development of methods to selectively stimulate TLR2 on Treg may lead to a novel approaches for the treatment of autoimmune diseases.

The Role of ICOS in Directing T Cell Responses : ICOS-Dependent Induction of T Cell Anergy by Tolerogenic Dendritic Cells

Tolerogenic dendritic cells (DC) play an important role in maintaining peripheral T cell tolerance in steady-state conditions through induction of anergic, IL-10-producing T cells with suppressive properties. ICOS, an activation-induced member of the CD28 family on T cells, is involved in the induction of IL-10, which itself could contribute to induction of anergy and development of suppressive T cells. Therefore, we analyzed the functional role of ICOS in the differentiation process of human CD4+ T cells upon their interaction with tolerogenic DC. We compared the functional properties of CD4+ T cells from healthy volunteers and ICOS-deficient patients after stimulation with tolerogenic DC. We report that induction of T cell anergy and suppressive capacity is completely blocked after knockdown of ICOS expression in T cells as well as after blocking of ICOS-ICOS ligand interaction in DC/T cell cocultures. Moreover, CD4+ T cells from ICOS-deficient patients were completely resistant to anergy induction and differentiation into suppressive T cells even after supplementation of IL-10. Furthermore, ICOS/ICOS ligand interaction stabilizes IL-10R expression on T cells and thus renders them sensitive to IL-10 effects. Taken together, these results indicate a crucial role for ICOS in the induction of peripheral tolerance maintained by tolerogenic DC mediated mostly via an IL-10-independent mechanism.

Dendritic Cells: Sentinels of Immunity and Tolerance

The induction of effective antigen-specific T-cell immunity to pathogens without the initiation of autoimmunity has evolved as a sophisticated and highly balanced immunoregulatory mechanism. This mechanism assures the generation of antigen-specific effector cells as well as the induction and maintenance of antigen-specific tolerance to self-structures of the body. As professional antigen-presenting cells of the immune system, dendritic cells (DC) are ideally positioned throughout the entire body and equipped with a unique capability to transport antigens from the periphery to lymphoid tissues. There is growing evidence that DC, besides their well-known immunostimulatory properties, also induce and regulate T-cell tolerance in the periphery. This regulatory function of DC is strictly dependent on their different stages of maturation and activation. Additionally, immunosuppressive agents and cytokines further influence the functions of maturing DC. The regulatory properties of DC include induction of T-cell anergy, apoptosis, and the generation of T-cells with regulatory capacities. This brief review summarizes the current knowledge about the immunoregulatory role of DC as guardians for the induction of T-cell immunity and tolerance.

Induction of strong and persistent MelanA/MART-1-specific immune responses by adjuvant dendritic cell-based vaccination of stage II melanoma patients

A significant percentage of stage II melanoma patients (tumor thickness >1 mm) remain at risk of tumor recurrence after primary tumor excision. In this study, we used tumor antigen‐pulsed dendritic cells as an adjuvant for immunization of these “high‐risk” melanoma patients after resection of the primary tumor. A total of 13 patients were included and vaccinated 6 times every 14 days with autologous dendritic cells pulsed with a MelanA/MART‐1 peptide in combination with a recall antigen. Antigen‐specific immune responses were monitored before, during and up to 1 year after the last vaccination. The majority of patients exhibited increased recall antigen‐specific CD4+ T cell responses upon vaccination. MelanA/MART‐1‐specific CD8+ T cells were expanded in 9/13 patients resulting in increased frequencies of memory cells in these patients. CD8+ T cells acquired the capacity to secrete IFN‐γ, to proliferate in culture in response to the tumor antigen used for vaccination and postvaccine samples contained MelanA/MART‐1‐specific T cells that recognized also the natural MelanA/MART‐1‐antigen expressed by tumor cells. Moreover, vaccination induced a long‐lived tumor antigen‐specific DTH‐reactivity in the majority of the patients, detectable even 12 months after the last immunization. These data demonstrate for the first time that vaccination with tumor antigen‐pulsed dendritic cells in a clinically adjuvant setting induces strong and persistent antigen‐specific T‐cell responses in tumor‐free stage II melanoma patients, suggesting that tumor protective T cell immunity can be achieved.

Single Base Mutation in the Fumarate Hydratase Gene Leading to Segmental Cutaneous Leiomyomatosis

recently been drawn to the possible interest of einacalcet. a calcimimetic drug that increases the sensitivity of PTH-secreting cells to extracellular calcium, resulting in a decrease of PTH production. This molecule is currently routinely used in end-stage renal failureassociated secondary hyperparathyroidism (4) and its efficiency in calciphylaxis has already been reported in two patients, in whom cutaneous lesions improved quickly after implementation of this treatment (I, 2). Similarly, a strikingly good and fast clinical result was observed in our observation. This favourable evolution is likely to be directly related to cinacalcet irealment.. since the dialysis parameters remained unchanged, and the clinical efficiency was correlated with a decrease in PTH level, but not with changes in calcium or phosphates rates. Moreover, in these three patients, the etlicacy and the rapidity of action of Cinacalcet appear to match the results obtained with parathyroid surgery. Accordingly, this molecule might be considered as a first-line option in patients with general contra-indication to surgery or when parathyroid surgery does not appear mandatory due to the mild nature of cutaneous lesions and/or to the limited PTH rate increase, as illustrated by our patient. Additionally, due to the risk of development of adynamic bone disease, this treatment should probably be restricted to patients with calciphylaxis and secondary hyperparathyroidism even though parathyroidectomy has been advoeated in patients with low PTH levels. Overall, this observation supports the concept of first-line treatment of end-stage renal failure-related calciphylaxis with cinacalcet in monotherapy in patients with secondary hyperparathyroidistn.

Spontaneous regression and recurrence in a case of nodular fasciitis.

Nodular fasciitis is a sporadic tumor that results from a benign proliferation of myofibroblasts in soft tissues. It presents clinically as a rapidly-growing firm nodule, most often localized in the subcutaneous tissue (1). While it may arise in any part of the body, there is a predilection for the upper extremities, especially the forearms (1–3). Nodular fasciitis occurs most commonly in younger adults, affecting males and females with equal frequency (2–4). Histologic diagnosis of these rapidly growing le-sions can be difficult owing to their dense cellularity and high mitotic activity; features shared with some sarcomas (2, 5, 6). Standard care consists of complete excision, and local recurrences occur very rarely (1–3). Spontaneous regression of nodular fasciitis has been reported, but there are only a few cases documented in the literature, and most often regression followed biopsy or incomplete excision of the lesion (7, 8). We describe here an unusual case of nodular fasciitis that regressed spontaneously and recurred after a 5-year interval.CASE REPORTA 30-year-old female physician presented for eva-luation of a solitary nodule on her left forearm. The lesion had grown to a maximal diameter of 1.5 cm over several days. There was no history of trauma. On clinical examination the nodule was firm, non-tender, well circumscribed, but seemed adherent to muscle. The lesion was not fixed to the overlying skin. The patient was otherwise healthy and there was no family history of dermal or connective tissue tumors. Interestingly, the patient described occurrence of a similar lesion at the exact same location on her left forearm 5 years earlier. This lesion had grown to a maximal diameter of ~2 cm over a several week period and had exhibited similar clinical features. The earlier tumor had regressed spontaneously over a several-week period, leaving an asymptomatic residual firm nodule ~2 mm in diameter. A clinical diagnosis of nodular fasciitis was made. The residual lesion did not change in size or character over a subsequent 5-year period.The rapid regrowth of this lesion was cause for concern and complete excision was recommended. The tumor was subsequently excised completely, together with surroun-ding subcutaneous tissue and an overlying ellipse of skin. Histologic evaluation of the surgical specimen revealed a small, circumscribed, but unencapsulated, nodular lesion comprised predominantly of spindle-shaped myofibro-blasts located in the subcutaneous fat (Fig. 1A). The lesion was confined to the subcutis and did not involve the overlying dermis or epidermis. Some myofibroblasts showed reactive changes, including plump nuclei and conspicuous nucleoli, but increased mitotic activity was not observed (Figs 1B and C). Immunohistochemical staining revealed that the tumor cells were positive for smooth muscle actin (SMA) (Fig. 1D), but negative for S-100, desmin and CD34 (not shown). The histologic diagnosis of a benign myofibroblastic proliferation confined to the subcutis was consistent with our clinical diagnosis of nodular fasciitis. The postoperative course was uneventful and local recurrence was not observed during a 6-month follow-up period. DISCUSSIONThe clinical course of our patient reveals two interesting features of nodular fasciitis: the spontaneous near-complete regression of the tumor without any antecedent manipulation, and subsequent local recurrence after a 5-year quiescent period. Regression of nodular fasciitis has been reported after fine needle aspiration biopsy, incisional biopsy or incomplete excision (7, 8). In these instances, it is difficult to determine if involution was “spontaneous” or if it was triggered by surgical interven-tion. Since gene expression profiles of nodular fasciitis lesions reveal upregulation of genes encoding inflamma-tory cytokines and chemokines in comparison with other types of fibroblastic entities (5), one could speculate that these lesions are poised to regress, or that they are inflamed and would eventually regress in the absence of definitive treatment. In our patient, since there was no manipulation of the original lesion, it is likely that the initial regression was truly spontaneous. Local recurrence of nodular fasciitis has rarely been reported. One of 250 patients in a large series expe-rienced a local recurrence (1), and another study repor-ted none in 15 patients (3) with an average follow-up period of 5.7 and 7.2 years, respectively. In contrast, a study describing 50 cases of nodular fasciitis of the external ear revealed a higher rate of local recurrence (9.3%), which was attributed to difficulties in obtaining clear surgical margins in the region around the ear (9). Of note, a detailed clinical-pathologic review of 134 cases of nodular fasciitis published more than 25 years ago reported that lesions recurred (18/134) only in patients who had been misdiagnosed initially (2). This study strongly supports the view that nodular fasciitis