Evaluation and characterization of the capability of dendritic cells generated by exposure of human peripheral blood monocytes to GM-CSF and IFN-alpha of inducing CD8 T cell priming and TH1 polarization

E’ stato dimostrato che l’IFN di tipo I agisce come “danger signal”, allertando il sistema immunitario sulla presenza di patogeni e promuovendo la conversione dei monociti in cellule presentanti l’antigene (APC) professionali. In studi precedenti abbiamo dimostrato che cellule dendritiche, ottenute da monociti trattati per 3 giorni con GM-CSF e IFN-alpha (IFN-DCs), posseggono un fenotipo parzialmente maturo. Le IFN-DCs si sono dimostrate più efficienti delle cellule dendritiche immature, ottenute con GM-CSF e IL-4, nell’indurre una risposta immunitaria di tipo TH1 e una risposta dei linfociti CD8 contro una serie di antigeni. Inoltre, le IFN-DCs sono altamente efficienti, rispetto alle IL4-DC maturate con il CD40L, nell’indurre cross-priming dei linfociti CD8 nei confronti di antigeni virali. Questa caratteristica si accompagna alla capacità di esprimere significativi quantitativi delle citochine IL23 e IL27. In studi recenti abbiamo dimostrato come le IFN-DCs siano capaci di indurre preferenzialmente una polarizzazione di tipo TH1 dei linfociti CD4 naive autologhi, stimolati con il superantigene SEA (staphylococcal enterotoxins A). Infatti, è stato possibile dimostrare come questi linfociti CD4 esprimano alte percentuali di marcatori CD25/CXCR3 e CD25/CD212 e producano consistenti quantità di IFN-γ. Queste caratteristiche sono accentuate quando le IFN-DCs sono pretrattate con l’Imiquimod, ligando del TLR7. Questi risultati suggeriscono che le IFN-DCs posseggano un’attitudine intrinseca a polarizzare la risposta CD4 verso il tipo di risposta TH1 e ad indurre priming dei linfociti CD8 in maniera particolarmente efficiente. Queste caratteristiche rendono le IFN-DCs candidati ideali quali adiuvanti cellulari per vaccinazioni terapeutiche in pazienti affetti da infezioni virali croniche o malattie neoplastiche.Type I IFNs (IFN-a/b) have recently been shown to act as danger signals, alerting the immune system of incoming pathogens and promoting monocyte conversion into professional antigen presenting cells. In particular, we previously demonstrated that highly active partially mature dendritic cells (DC) can be generated from human monocytes after a single step of 3-day culture with IFN-a/GM-CSF (IFN-DC). In our studies, IFN-DC proved to be more efficient than immature DC generated in the presence of GM-CSF and IL-4 in inducing a TH-1 type of immune response and CD8+ T cell responses against defined antigens in different models. Moreover, we recently reported that IFN-DC are highly effective, and superior to CD40L-matured IL-4-DC, in inducing cross-priming of CD8+ T cells against viral antigens. This property correlated with enhanced potential to express the specific subunits of the IL-23 and IL-27 cytokines. Altogether, these results suggest that IFN-DC are directly licensed for an efficient CD8+ T cell priming and possess a special attitude to bias the T cell response toward a TH1 type. These features render IFN-DC particularly attractive candidates as cellular adjuvants for the therapeutic vaccination in patients with cancer and severe chronic infectious diseases. We are now studying the interactions between IFN-DC and autologous naïve CD4+ T cells in order to gain insight into the mechanisms of TH1 polarization by IFN-DC. Higher percentages of cells co-expressing CD25/CXCR3 and CD25/CD212 (activated TH1 cells) have been detected in cultures of naïve CD4+ T cells exposed to SEA in the presence of autologous IFN-DC for 7 days, as compared to the cultures with conventional DC. The intracellular staining for IFN-γ and IL-4 expression has revealed an intrinsic attitude of IFN-DC to induce higher numbers of IFNγ-producing CD4. These features are further enhanced when IFN-DC are pre-treated with the TLR7 ligand Imiquimod. All these properties correlate with an enhanced potential of IFN-DC to express cytokine of the IL-12 cytokine family, further confirming our previous findings