Misuse and overuse of antibiotics have contributed in the last decades to a phenomenon known as antibiotic resistance which is currently considered one of the principal threats to global public ...health by the World Health Organization. The aim to find alternative drugs has been demonstrated as a real challenge. Thanks to their biodiversity, insects represent the largest class of organisms in the animal kingdom. The humoral immune response includes the production of antimicrobial peptides (AMPs) that are released into the insect hemolymph after microbial infection. In this review, we have focused on insect immune responses, particularly on AMP characteristics, their mechanism of action and applications, especially in the biomedical field. Furthermore, we discuss the Toll, Imd, and JAK-STAT pathways that activate genes encoding for the expression of AMPs. Moreover, we focused on strategies to improve insect peptides stability against proteolytic susceptibility such as D-amino acid substitutions, N-terminus modification, cyclization and dimerization.
In recent years a novel concept has emerged indicating that the actual role of natural killer (NK) cells is not confined to the destruction of virus-infected cells or tumors. Indeed, different NK ...subsets exist that display major functional differences in their cytolytic activity, cytokine production and homing capabilities. In particular, CD56(high) CD16(-) NK cells that largely predominate in lymph nodes, have little cytolytic activity but release high levels of cytokines whereas CD56(low) CD16(+) NK cells that predominate in peripheral blood and inflamed tissues, display lower cytokine production, but potent cytotoxicity. The latter is characterized by granule polarization and exocytosis of various proteins including perforin and granzymes that mediate target cell killing. The recruitment of CD56(low) CD16(+) NK cells into inflamed peripheral tissues is orchestrated by various chemochines including the newly identified Chemerin. At these sites, NK cells, upon engagement of different triggering receptors become activated and upregulate their cytokine production and cytotoxicity after interaction with myeloid dendritic cells (DCs). Importantly, during this interaction NK cells also mediate the 'editing' of DCs undergoing maturation. This process appears to play a crucial role in shaping both innate and adaptive immune responses. Indeed, only DCs undergoing this NK-mediated quality control would become fully mature and capable of inducing priming of protective Th1 responses.
NK cells are important players of the early innate defense against various pathogens. In this study, we investigated the interaction between human NK cells and Mycobacterium bovis bacille ...Calmette–Guérin (BCG) and we determined whether and how such an interaction might impact on NK cell activation, cytokine production and cytotoxicity. We show that highly purified NK cells, upon short-term co-culture with BCG, expressed activation markers including CD69 and CD25. Moreover, these NK cells released IFN-gamma and tumor necrosis factor-alpha and killed more efficiently different targets including monocyte-derived immature dendritic cell. All these functions were strongly up-regulated in the presence of exogenous IL-12. Although more efficient responses were detected in NK cell populations displaying an NCRbright phenotype, no direct evidence of an involvement of triggering NK receptors in BCG recognition could be obtained. On the other hand, anti-toll-like receptor (TLR)2 mAb inhibited NK cell responses to BCG, suggesting that NK cells may express a functional TLR2, which plays a role in their mechanism of direct BCG recognition. Taken together, these data suggest that BCG, by inducing simultaneous activation of NK and antigen-presenting cells via their ‘shared’ TLR2, can promote efficient bidirectional NK–dendritic cell interactions necessary for subsequent priming of Th1 responses.
Natural killer cells can discriminate between normal cells and cells that do
not express adequate amounts of major histocompatibility complex (MHC) class I
molecules. The discovery, both in mouse and ...in human, of MHC-specific
inhibitory receptors clarified the molecular basis of this important NK cell
function. However, the triggering receptors responsible for positive NK cell
stimulation remained elusive until recently. Some of these receptors have now
been identified in humans, thus shedding some light on the molecular mechanisms
involved in NK cell activation during the process of natural cytotoxicity.
Three novel, NK-specific, triggering surface molecules (NKp46, NKp30, and
NKp44) have been identified. They represent the first members of a novel
emerging group of receptors collectively termed natural cytotoxicity receptors
(NCR). Monoclonal antibodies (mAbs) to NCR block to differing extents the
NK-mediated lysis of various tumors. Moreover, lysis of certain tumors can be
virtually abrogated by the simultaneous masking of the three NCRs. There is a
coordinated surface expression of the three NCRs, their surface density varying
in different individuals and also in the NK cells isolated from a given
individual. A direct correlation exists between the surface density of NCR and
the ability of NK cells to kill various tumors. NKp46 is the only NCR involved
in human NK-mediated killing of murine target cells. Accordingly, a homologue
of NKp46 has been detected in mouse. Molecular cloning of NCR revealed novel
members of the Ig superfamily displaying a low degree of similarity to each
other and to known human molecules. NCRs are coupled to different signal
transducing adaptor proteins, including CD3ζ, Fc∍RIγ, and
KARAP/DAP12. Another triggering NK receptor is NKG2D. It appears to play either
a complementary or a synergistic role with NCRs. Thus, the triggering of NK
cells in the process of tumor cell lysis may often depend on the concerted
action of NCR and NKG2D. In some instances, however, it may uniquely depend
upon the activity of NCR or NKG2D only. Strict NKG2D-dependency can be
appreciated using clones that, in spite of their NCR
dull
phenotype,
efficiently lyse certain epithelial tumors or leukemic cell lines. Other
triggering surface molecules including 2B4 and the novel NKp80 appear to
function as coreceptors rather than as true receptors. Indeed, they can induce
natural cytotoxicity only when co-engaged with a triggering receptor. While an
altered expression or function of NCR or NKG2D is being explored as a possible
cause of immunological disorders, 2B4 dysfunction has already been associated
with a severe form of immunodeficiency. Indeed, in patients with the X-linked
lymphoproliferative disease, the inability to control Epstein-Barr virus
infections may be consequent to a major dysfunction of 2B4 that exerts
inhibitory instead of activating functions.
A number of experimental studies have shown that natural killer (NK) cells can eliminate cancer cells and the mechanisms involved in this effect have been uncovered during the last two decades. ...Clinical data from haploidentical haematopoietic stem cell transplantation (haplo-HSCT) revealed that NK cells were responsible for remarkably favourable effects in both adult and paediatric high-risk leukaemias. NK receptors specific for major histocompatibility complex (MHC) class I molecules, including killer immunoglobulin (Ig)-like receptors (KIR) and CD94/NKG2A, play a major role in the anti-leukaemia effect (mediating either inhibitory or activating signals). Haplo- HSCT requires a heavy conditioning regimen for the patient and the use of large numbers of T cell-depleted HSC to be grafted. After transplantation, natural killer cells develop from HSC shortly after engraftment and may include 'alloreactive' NK cells that kill leukaemic cells and prevent graft-versus-host disease (GvHD). Alloreactive NK cells are characterized by the expression of KIR that are not engaged by any of the human leucocyte antigen (HLA) class I alleles expressed by the patient. Their generation is dependent upon the existence of a KIR/HLA class I mismatch between donor and recipient. Novel important information on the function and specificity of different KIR has been obtained recently by the analysis of donor-derived alloreactive NK cells in a cohort of paediatric patients given haplo-HSCT to cure acute, high-risk leukaemias.
The treatment of Epstein‐Barr virus (EBV)‐related post‐transplant lymphoproliferative disease (PTLD) after hematopoietic stem cell transplantation (HSCT) is still unsatisfactory. We conducted a ...prospective trial to evaluate the impact of routine EBV surveillance and preemptive treatment with the anti‐CD20 monoclonal antibody rituximab on the development of PTLD in pediatric recipients of extensively T‐cell depleted HSCT from an HLA‐haploidentical relative. Twenty‐seven patients were included in the surveillance program, 12 developed EBV DNA positivity, with 8 of 12 presenting with sustained viral DNA levels requiring treatment with rituximab. Treatment was well tolerated, and induced clearance of EBV DNA in all patients. However, 4/8 patients showed a new increase in EBV load, coincident with the emergence of CD20−/CD19+ B cells in peripheral blood, accompanied by overt PTLD in 3 patients. The latter cleared PTLD after receiving donor EBV‐specific cytotoxic T‐lymphocytes (CTLs), and persist in remission at a median 30‐month follow‐up. EBV‐specific T‐cell frequency, undetectable at time of EBV DNA positivity, was restored by T‐cell therapy to levels comparable with controls. We conclude that preemptive therapy with rituximab is safe, but only partly effective in haplo‐HSCT recipients. Patients who progress to PTLD under rituximab treatment can be rescued permanently by infusion of EBV‐specific CTLs.
Three patients who progressed to overt PTLD responded to donor EBV‐specific cytotoxic T cell infusion and remain in remission.
In humans, natural killer (NK) cell function is regulated by a series of receptors and coreceptors with either triggering or inhibitory activity. Here we describe a novel 60-kD glycoprotein, termed ...NTB-A, that is expressed by all human NK, T, and B lymphocytes. Monoclonal antibody (mAb)-mediated cross-linking of NTB-A results in the induction of NK-mediated cytotoxicity. Similar to 2B4 (CD244) functioning as a coreceptor in the NK cell activation, NTB-A also triggers cytolytic activity only in NK cells expressing high surface densities of natural cytotoxicity receptors. This suggests that also NTB-A may function as a coreceptor in the process of NK cell activation. Molecular cloning of the cDNA coding for NTB-A molecule revealed a novel member of the immunoglobulin superfamily belonging to the CD2 subfamily. NTB-A is characterized, in its extracellular portion, by a distal V-type and a proximal C2-type domain and by a cytoplasmic portion containing three tyrosine-based motifs. NTB-A undergoes tyrosine phosphorylation and associates with the Src homology 2 domain–containing protein (SH2D1A) as well as with SH2 domain–containing phosphatases (SHPs). Importantly, analysis of NK cells derived from patients with X-linked lymphoproliferative disease (XLP) showed that the lack of SH2D1A protein profoundly affects the function not only of 2B4 but also of NTB-A. Thus, in XLP-NK cells, NTB-A mediates inhibitory rather than activating signals. These inhibitory signals are induced by the interaction of NTB-A with still undefined ligands expressed on Epstein-Barr virus (EBV)-infected target cells. Moreover, mAb-mediated masking of NTB-A can partially revert this inhibitory effect while a maximal recovery of target cell lysis can be obtained when both 2B4 and NTB-A are simultaneously masked. Thus, the altered function of NTB-A appears to play an important role in the inability of XLP-NK cells to kill EBV-infected target cells.
Mesenchymal stromal cells are employed in various different clinical settings in order to modulate immune response. However, relatively little is known about the mechanisms responsible for their ...immunomodulatory effects, which could be influenced by both the cell source and culture conditions.
We tested the ability of a 5% platelet lysate-supplemented medium to support isolation and ex vivo expansion of mesenchymal stromal cells from full-term umbilical-cord blood. We also investigated the biological/functional properties of umbilical cord blood mesenchymal stromal cells, in comparison with platelet lysate-expanded bone marrow mesenchymal stromal cells.
The success rate of isolation of mesenchymal stromal cells from umbilical cord blood was in the order of 20%. These cells exhibited typical morphology, immunophenotype and differentiation capacity. Although they have a low clonogenic efficiency, umbilical cord blood mesenchymal stromal cells may possess high proliferative potential. The genetic stability of these cells from umbilical cord blood was demonstrated by a normal molecular karyotype; in addition, these cells do not express hTERT and telomerase activity, do express p16(ink4a) protein and do not show anchorage-independent cell growth. Concerning alloantigen-specific immune responses, umbilical cord blood mesenchymal stromal cells were able to: (i) suppress T- and NK-lymphocyte proliferation, (ii) decrease cytotoxic activity and (iii) only slightly increase interleukin-10, while decreasing interferon-gamma secretion, in mixed lymphocyte culture supernatants. While an indoleamine 2,3-dioxygenase-specific inhibitor did not reverse mesenchymal stromal cell-induced suppressive effects, a prostaglandin E(2)-specific inhibitor hampered the suppressive effect of both umbilical cord blood- and bone marrow-mesenchymal stromal cells on alloantigen-induced cytotoxic activity. Mesenchymal stromal cells from both sources expressed HLA-G.
Umbilical cord blood- and bone marrow-mesenchymal stromal cells may differ in terms of clonogenic efficiency, proliferative capacity and immunomodulatory properties; these differences may be relevant for clinical applications.
Natural killer (NK) cells have been known for many years as the lymphocyte subset characterized by the highest cytolytic potential against virus-infected and tumor-transformed cells. A surprisingly ...high number of surface molecules have been recognized that regulate human NK cell function. These include MHC-specific inhibitory receptors, which impair NK cells’ ability to attack normal self-tissues, and activating receptors and coreceptors that allowthemto recognize and kill transformed cells. The recent identification of some of the cellular ligands specifically recognized by these receptors/coreceptors contributes to elucidation of the mystery of the role played by NK cells in immune responses.
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