Maria Pepe

Toll-Like Receptor Signaling Mechanisms Involved in Dendritic Cell Activation: Potential Therapeutic Control of T Cell Polarization

Dendritic cells (DCs) represent a bridge between innate and adaptive immunity, being the maturation process dependent on the binding of pathogen-associated molecular patterns (PAMPs) to Toll-Like Receptors (TLRs) expressed on their surface. TLRs associated to adaptor proteins, following binding to PAMPs, are able to skew specific immune responses towards the T helper (h)(1)- or the Th(2)-type according to the antigenic stimulation involved. Of note, other receptors different from TLRs are expressed on DCs which are also able to recognize PAMPs. Among them, one should mention the DC-specific ICAM-3-grabbing nonintegrin, the mannose receptor, Dectin-1 (the major beta-glucan receptor) and NOD2. Finally, the possibility to interfere therapeutically with the TLR-dependent and -independent signaling pathways in DCs is reviewed. According to current literature, DC activation, their antigen uptake capacity and migration can be enhanced with different experimental procedures whose use in humans is still under evaluation. However, just recently a probiotic cocktail VSL3, successfully used in patients with pouchitis, seems to act on DCs, promoting abundant release of Interleukin-10 in the gut. These novel therapeutic strategies based on the modulation of the signaling pathways in DCs seem to be encouraging for the treatment of inflammatory and autoimmune diseases.

Immune responses to fungal infections and therapeutic implications.

Host responses to fungi result from a coordinate interplay between innate and adaptative immune system. Neutrophils and monocytes are involved in the non specific clearance of yeasts (e.g. Candida albicans and Cryptococcus neoformans), while T helper 1 type responses are protective via release of interferon gamma. By contrast, T helper 2 responses (IL-4 and IL 10 release) correlate with disease exacerbation and pathology. IL-12 production which enhances T helper 1 type responses seem to exert a beneficial role in the course of Candida infection. In particular, its production from neutrophilis may support memory T helper 1 cell responses of the fungus. With respect to anti-Candida vaccines several approaches are in progress, such as use of heat-killed Candida albicans in combination with adjuvants, purified peptides and proteins and immunogenic peptide-lipid conjugates. Furthermore, exogenous IL-12 may play an important role in inducing a T helper 1 anticandidal response, also replacing neutrophils in neutropenic patients. At the same time, granulocyte-colony stimulating factor has exhibited therapeutic efficacy in experimental and human models of fungal infection.

Allergic Contact Dermatitis with a Fertilizer Containing Hydrogen Cyanamide (Dormex

Cyanamide is a chemical substance used in the treatment of chronic alcoholism as well in agriculture as a fertilizer. We report the case of a 28-year-old healthy non-atopic man that developed a severe skin eruption after the accidental penetration of a small amount of Dormex® (a plant growth regulator containing cyanamide) through the patients gloves. Patch tests revealed positive reactions to Dormex® 1% pet. and cyanamide at a dilution of 0.1% pet. and 1% pet. We discuss the causes of sensitization in a patients that regularly used protective measures during anti-parasites treatments.

A comparative study between conventional and laparoscopic cholecystectomy: evaluation of phagocytic and T-cell-mediated antibacterial activities.

Over the past few years, many reports have pointed out that open, but not minimally invasive, cholecystectomy was associated with reduced immune functions. Also, after laparoscopic surgery, a reduced impairment of T cell functions and lower levels of proinflammatory cytokines, epinephrine, and norepinephrine were found in comparison with those detected in patients who underwent conventional cholecystectomy. We investigated polymorphonuclear cell- and monocyte-mediated phagocytosis and killing and T-cell-mediated antibacterial activity in 12 patients who underwent open cholecystectomy versus another group of 12 patients who underwent laparoscopic cholecystectomy. Our data show that polymorphonuclear and monocyte killing activities are preserved or are less affected in patients who undergo laparoscopy when compared with patients who undergo conventional operation. On the other hand, in both groups of patients, T-cell-mediated antibacterial activity was significantly reduced in the preoperative period, and, therefore, we could not draw conclusions on the effects of the surgical techniques used on the above immune parameter. The overall data suggest that laparoscopic cholecystectomy is a valid alternative to open surgery because of the moderate postoperative immune suppression and decreased risk of postsurgical infections.

In Vitro Infection of Human Monocyte-Derived Dendritic Cells with Candida albicans: Receptorial Involvement and Therapeutic Implications

Nowadays, infections with Candida albicans (C.a.) are very frequent, mostly in the so-called immunocompromised host. Therefore, research has been focused on the types of immune response elicited by C.a., with the aim to develop novel therapeutic strategies. Neutrophils and macrophages (MØ) are deeply involved in the host defense against C.a., and also dendritic cells (DCs) seem to be very active in the host protection. In particular, DCs display an array of surface receptors able to interact with fungal components, even including Toll-like receptors. Here, we will illustrate the in vitro immune response of human monocyte-derived DCs infected with C.a. In this test system, DCs exert phagocytic and killing activities with a magnitude similar to that of MØ. Moreover, in the presence of autologous CD4(+) cells, DCs produce T-helper (h) 1 type cytokines. This Th1 polarizing activity is mediated by interleukin-12 released by infected CDs in the presence of CD4(+) cells. Taken together, these data suggest a protective role played by DCs in the course of C.a. infection and the possibility to develop new strategies of immune intervention.

Toll-like receptor-positive cells and recognition of pathogens: how human myeloid dendritic cells respond to in vitro infection with Leishmania infantum.

Dendritic cells (DCs), instructed by the priming signals from microbial factors, can produce interleukin (IL)-12p70 and promote T helper (Th)1 proliferation and interferon (IFN)-gamma production. This event seems to be critical for the containment of infections caused by intracellular pathogens, even including Leishmania infection. In the present in vitro study we have investigated: 1) phagocytic capacities and IL-12 production by human monocyte-derived DCs and macrophages (MØs), infected with Leishmania infantum promastigotes; 2) IFN-gamma production by human CD4+ T cells co-incubated with DCs or macrophages pulsed with live promastigotes. Monocyte-derived myeloid DCs and MØs from healthy donors were infected with live metacyclic Leishmania infantum (MON-1) promastigotes, previously opsonized with 5% autologous serum, at 1:4 cell/parasite ratio. Percentage and index of phagocytosis were calculated after 2, 24 and 48 h of incubation. IL-12 production was evaluated by an ELISA in supernatants from 48 h Leishmania-infected or lipopolysaccharides (LPS)-stimulated DCs and MØs, also in the presence of phytohemagglutinin-activated or inactivated CD4+ T cells. For IFN-gamma production, CD4+ T cells were repeatedly stimulated with DCs or MØs, pulsed with live Leishmania promastigotes or activated with LPS. The number of IFN-gamma-secreting cells was evaluated by an ELISpot assay. Results showed that MØs have a higher phagocytic capacity towards L. infantum promastigotes than DCs. Moreover, unlike MØs, Leishmania-infected DCs were able to release IL-12p70; this production significantly increased in the presence of activated CD4+ T cells. Finally, DCs pulsed with live parasites and added to autologous CD4+ T cells induced a higher number of IFN-gamma-secreting cells than MØs, thus indicating their ability to polarize Th cells toward the Th1 subset. These data indicate that DCs are able to promote protective Th1 immune responses in our experimental model of Leishmania infantum infection, thus representing the grounds for initiating immunoterapeutic and vaccinal strategies.

Contact dermatitis with clostridiopeptidase A contained in Noruxol® ointment

Clostridiopeptidase A, also called collagenase 1, is a proteolytic enzyme capable of digesting collagen. Preparations containing clostridiopeptidase A are used topically for the debridement of dermal ulcers, burns and other necrotic lesions to facilitate the formation of granulation tissue and subsequent epithelization. We observed 4 patients with a periulcerative eczema after repeated applications of Noruxol® ointment (Smith & Nephew Ltd, L Hull, UK). Patch testing with Noruxol® ointment as is and its excipients (soft paraffin and white petrolatum), as well as scaled dilutions of the main ingredient of this topical preparation, clostridiopeptidase A (Firma, Florence, Italy), showed doubtful reactions to Noruxol® ointment in 3 patients and a positive reactions only in 1 patient. All patients showed positive reactions to clostridiopeptidase A 1% in pet. This study shows the sensitizing capacity of clostridiopeptidase A that should be tested in all patients with suspect sensitization to Noruxol® ointment.

A syndrome characterized by psychiatric disorders, recurrent mucosal infections and natural immunity deficits: clinical approach.

The authors summarize their own previous work on the identification of a subset of patients characterized by psychiatric disorders, recurrency of mucosal infections and impaired natural immunity. The diagnostic approach to these patients based on the close collaboration between infectivologists, immunologists and psychiatrists is described with the aim to find out combined treatments for the amelioration of clinical manifestations.