Exosomes are nanovesicles released by normal and tumor cells, which are detectable in cell culture supernatant and human biological fluids, such as plasma. Functions of exosomes released by “normal” cells are not well understood. In fact, several studies have been carried out on exosomes derived from hematopoietic cells, but very little is known about NK cell exosomes, despite the importance of these cells in innate and adaptive immunity. In this paper, we report that resting and activated NK cells, freshly isolated from blood of healthy donors, release exosomes expressing typical protein markers of NK cells and containing killer proteins (i.e., Fas ligand and perforin molecules). These nanovesicles display cytotoxic activity against several tumor cell lines and activated, but not resting, immune cells. We also show that NK-derived exosomes undergo uptake by tumor target cells but not by resting PBMC. Exosomes purified from plasma of healthy donors express NK cell markers, including CD56+ and perforin, and exert cytotoxic activity against different human tumor target cells and activated immune cells as well. The results of this study propose an important role of NK cell-derived exosomes in immune surveillance and homeostasis. Moreover, this study supports the use of exosomes as an almost perfect example of biomimetic nanovesicles possibly useful in future therapeutic approaches against various diseases, including tumors.

Recent characterization of abnormal phosphatidylcholine metabolism in tumor cells by nuclear magnetic resonance (NMR) has identified novel fingerprints of tumor progression that are potentially useful as clinical diagnostic indicators. In the present study, we analyzed the concentrations of phosphatidylcholine metabolites, activities of phosphocholineproducing enzymes, and uptake of [methyl-14 C]choline in human epithelial ovarian carcinoma cell lines (EOC) compared with normal or immortalized ovary epithelial cells (EONT). Quantification of phosphatidylcholine metabolites contributing to the 1 H NMR total choline resonance (3.20-3.24 ppm) revealed intracellular [phosphocholine] and [total choline] of 2.3 F 0.9 and 5.2 F 2.4 nmol/10 6 cells, respectively, with a glycerophosphocholine/phosphocholine ratio of 0.95 F 0.93 in EONT cells; average [phosphocholine] was 3-to 8-fold higher in EOC cells (P < 0.0001), becoming the predominant phosphatidylcholine metabolite, whereas average glycerophosphocholine/phosphocholine values decreased significantly to V0.2. Two-dimensional {phosphocholine/total choline, [total choline]} and {glycerophosphocholine/total choline, [total choline]} maps allowed separate clustering of EOC from EONT cells (P < 0.0001, 95% confidence limits). Rates of choline kinase activity in EOC cells were 12-to 24-fold higher (P < 0.03) than those in EONT cells (basal rate, 0.5 F 0.1 nmol/10 6 cells/h), accounting for a consistently elevated (5-to 15-fold) [methyl-14 C]-choline uptake after 1-hour incubation (P < 0.0001). The overall activity of phosphatidylcholine-specific phospholipase C and phospholipase D was also higher (f5-fold) in EOC cells, suggesting that both biosynthetic and catabolic pathways of the phosphatidylcholine cycle likely contribute to phosphocholine accumulation. Evidence of abnormal phosphatidylcholine metabolism might have implications in EOC biology and might provide an avenue to the development of noninvasive clinical tools for EOC diagnosis and treatment follow-up. (Cancer Res 2005; 65(20): 9369-76)

Successful chemotherapy accounts for both tumor-related factors and host immune response. Compelling evidence suggests that some chemotherapeutic agents can induce an immunogenic type of cell death stimulating tumor-specific immunity. Here, we show that cyclophosphamide (CTX) exerts two types of actions relevant for the induction of antitumor immunity in vivo: (i) effect on dendritic cell (DC) homeostasis, mediated by endogenous type I interferons (IFN-I), leading to the preferential expansion of CD8a þ DC, the main subset involved in the cross-presentation of cell-derived antigens; and (ii) induction of tumor cell death with clear-cut immunogenic features capable of stimulating tumor infiltration, engulfment of tumor apoptotic material, and CD8 T-cell cross-priming by CD8a þ DC. Notably, the antitumor effects of CTX were efficiently amplified by IFN-I, the former providing a source of antigen and a "resetting" of the DC compartment and the latter supplying optimal costimulation for T-cell cross-priming, resulting in the induction of a strong antitumor response and tumor rejection. These results disclose new perspectives for the development of targeted and more effective chemoimmunotherapy treatments of cancer patients. Cancer Res; 71(3); 768-78. Ó2010 AACR.

Chronic inflammation of the lung, as a consequence of persistent bacterial infections by several opportunistic pathogens represents the main cause of mortality and morbidity in cystic fibrosis (CF) patients. Mechanisms leading to increased susceptibility to bacterial infections in CF are not completely known, although the involvement of cystic fibrosis transmembrane conductance regulator (CFTR) in microbicidal functions of macrophages is emerging. Tissue macrophages differentiate in situ from infiltrating monocytes, additionally, mature macrophages from different tissues, although having a number of common activities, exhibit variation in some molecular and cellular functions. In order to highlight possible intrinsic macrophage defects due to CFTR dysfunction, we have focused our attention on in vitro differentiated macrophages from human peripheral blood monocytes. Here we report on the contribution of CFTR in the bactericidal activity against Pseudomonas aeruginosa of monocyte derived human macrophages. At first, by real time PCR, immunofluorescence and patch clamp recordings we demonstrated that CFTR is expressed and is mainly localized to surface plasma membranes of human monocyte derived macrophages (MDM) where it acts as a cAMP-dependent chloride channel. Next, we evaluated the bactericidal activity of P. aeruginosa infected macrophages from healthy donors and CF patients by antibiotic protection assays. Our results demonstrate that control and CF macrophages do not differ in the phagocytic activity when infected with P. aeruginosa. Rather, although a reduction of intracellular live bacteria was detected in both non-CF and CF cells, the percentage of surviving bacteria was significantly higher in CF cells. These findings further support the role of CFTR in the fundamental functions of innate immune cells including eradication of bacterial infections by macrophages.

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by fibrosis and vasculopathy. CXCL4 represents an early serum biomarker of severe SSc and likely contributes to inflammation via chemokine signaling pathways, but the exact role of CXCL4 in SSc pathogenesis is unclear. Here, we elucidate an unanticipated mechanism for CXCL4-mediated immune amplification in SSc, in which CXCL4 organizes “self” and microbial DNA into liquid crystalline immune complexes that amplify TLR9-mediated plasmacytoid dendritic cell (pDC)-hyperactivation and interferon-α production. Surprisingly, this activity does not require CXCR3, the CXCL4 receptor. Importantly, we find that CXCL4-DNA complexes are present in vivo and correlate with type I interferon (IFN-I) in SSc blood, and that CXCL4-positive skin pDCs coexpress IFN-I-related genes. Thus, we establish a direct link between CXCL4 overexpression and the IFN-I-gene signature in SSc and outline a paradigm in which chemokines can drastically modulate innate immune receptors without being direct agonists.

We investigated the effect of interleukin (IL)-2, a T cell growth factor capable of activating certain macrophage functions, on interferon (IFN)-gamma expression in resting mouse peritoneal macrophages (PM). IL-2 addition to PM from different mouse strains up-modulated IFN-gamma mRNA and protein secretion. It is notable that endogenous type I and II IFNs did not play any role in the IL-2-mediated effect, as comparable levels of secreted IFN-gamma were observed upon IL-2 stimulation of PM from deficient mice. In contrast, endogenous IFN-gamma was requested for the IL-12-induced IFN-gamma production. It is interesting that blocking of each component of the IL-2 receptor (IL-2R) by neutralizing antibodies almost completely abolished IL-2-induced IFN-gamma production, suggesting that all IL-2R chains contribute to the PM biological response to IL-2. The simultaneous treatment of PM with IL-2 and IL-12 resulted in a higher IFN-gamma secretion with respect to that obtained upon treatment with IL-2 or IL-12 alone. It is notable that IFN-gamma protein was expressed intracellularly in the majority of cells exhibiting a macrophage phenotype (i.e., F4/80+) and was secreted upon IL-2 stimulation. Overall, these findings demonstrate that IL-2 regulates at different levels IFN-gamma expression in macrophages, highlighting the crucial role of these cells and their regulated responsiveness to key cytokines in the cross-talk between innate and adaptive immunity.

IntroductionOver the past years, it has become apparent that type-I interferons (IFNs) affect adaptive immunity through their effects on monocytes. In particular, IFN-␣ has been shown to act as a potent inducer of the rapid differentiation of human monocytes into highly activated and partially mature dendritic cells (DCs), known as IFN-DCs. 1 We demonstrated previously that human monocytes exposed to granulocyte macrophage colony-stimulating factor (GM-CSF) and IFN-␣ are rapidly induced to express a set of membrane molecules involved in antigen (Ag) presentation and T-cell costimulation, as well as to strongly promote T helper (Th)-1 response and CD8 ϩ T cell cross-priming. 2 Moreover, IFN-DCs were shown to cross-present very efficiently low amounts of nonstructural-3 protein (NS3) of hepatitis C virus (HCV) to a specific CD8 ϩ T cell clone, even in the absence of CD4 ϩ T-cell help. 2 The cross-presentation efficiency of DCs is not dictated solely by their Ag capture capability 3 ; it also is affected by critical factors such as (1) the route of Ag uptake, (2) acidification-sensitive Ag degradation in endosomal-lysosomal compartments, and (3) Ag entry into the major histocompatibility complex class-I (MHC-I) pathway. [4][5][6][7][8] At present, 4 nonmutually exclusive models have been proposed to explain cross-presentation. [8][9][10] In the canonical cytosolic pathway, endocytosed Ags are translocated into the cytosol, where they are degraded by the proteasome, and then the antigenic peptides are transported into the lumen of the endoplasmic reticulum (ER) by the transporters associated with Ag processing (TAPs), 9,10 or alternatively, reimported from the cytoplasm into the early endosomes and loaded onto endosomal 12 According to a less well-defined TAP-and proteasomeindependent endosomal pathway, Ags can be processed by endosomal proteases and loaded onto MHC-I molecules directly within early and late endosomes and lysosomes. [13][14][15] An additional model involves the delivery of components of the ER to endocytic organelles or the transport of incoming Ags to the ER. [16][17][18] Here, we have investigated the mechanisms underlying the superior efficiency of IFN-DCs in the cross-presentation of soluble proteins, by studying (1) the Ag uptake and trafficking to the class-I processing pathway, (2) the maturation kinetic of the organelles containing the internalized proteins, (3) the Ag stability within endosomes, and (4) the Ag processing and cross-presentation to specific CD8 ϩ T cells. The results reveal that IFN-DCs exhibit a delayed endosomal acidification associated with a prolonged Ag survival and retention in the early endosomal compartment, as well as with Ag trafficking to recycling pathways. In IFN-DCs, both early and recycling endosomal compartments serve as important stores of MHC-I molecules, allowing rapid presentation of exogenous Ags. These findings provide novel mechanistic insight into the cross-presentation efficiency of IFN-DCs and underscore the potential advantage of using these cellula...

Caveolin-1 (Cav-1), a member of the caveolin family, regulates caveolae-associated signaling proteins, which are involved in many biological processes, including cancer development. Cav-1 was found to exert a complex and ambiguous role as oncogene or tumor suppressor depending on the cellular microenvironment.Here we investigated Cav-1 expression and function in a panel of melanomas, finding its expression in all the cell lines. The exception was the primary vertical melanoma cell line, WM983A, characterized by the lack of Cav-1, and then utilized as a recipient for Cav-1 gene transduction to address a series of functional studies.The alleged yet controversial role of phospho (Ph)-Cav-1 on cell regulation was also tested by transducing the nonphosphorylatable Cav-1Y14A mutant. Wild-type Cav-1, but not mutated Cav-1Y14A, increased tumorigenicity as indicated by enhanced proliferation, migration, invasion and capacity of forming foci in semisolid medium. Accordingly, Cav-1 silencing inhibited melanoma cell growth reducing some of the typical traits of malignancy. Finally, we detected a secreted fraction of Cav-1 associated with cell released microvesicular particles able to stimulate in vitro anchorage independence, migration and invasion in a paracrine/ autocrine fashion and, more important, competent to convey metastatic asset from the donor melanoma to the less aggressive recipient cell line. A direct correlation between Cav-1 levels, the amount of microvesicles released in the culture medium and MMP-9 expression was also observed. ' UICCKey words: melanoma; caveolin-1; microvesicles; tumorigenicity Caveolin-1 (Cav-1) is a 22-24 kDa protein originally identified as a structural component of caveolae, specialized invaginations of the plasma membrane. These caveolae represent compartments in which key signaling transduction molecules are concentrated to provide an efficient system for cellular cross talk. Through its ''scaffold domain'' Cav-1 is able to self-interact and to regulate the activity of other caveolae-associated signaling proteins. 1 When Cav-1 was evaluated for its expression in human cancer cell lines and tumor samples of different origin, the outcome was ambiguous. The observed expression profiles indicated that the role of Cav-1 varied according to tumor types. 2,3 Although its growth inhibitory action has been clearly demonstrated in vivo in Cav-12/2 mice, 4 more recent data supported the direct correlation between Cav-1 expression level and tumor aggressiveness 5 and, in some cases, with a poorer clinical outcome. 6 Hence Cav-1 apparently possesses mutually exclusive functions, as tumor suppressor or tumor-promoting gene, depending on tumor type/stage, cell context and the deriving availability of Cav-1 interacting partners. A specific example indicating the importance of Cav-1 partnership involves the formation of a Cav-1/E-cadherin (E-cad) complex at the plasma membrane. In primary cancer cells, where E-cad is generally expressed, Cav-1 exerts its antiproliferative and proapoptotic propertie...