Immunohistochemical analysis of FOXP3 in primary breast tumors showed that a high number of tumor-infiltrating regulatory T cells (Ti-Treg) within lymphoid infiltrates surrounding the tumor was predictive of relapse and death, in contrast to those present within the tumor bed. + , and CD8 + T cells was documented within lymphoid infiltrates. Altogether, these results show that Treg are selectively recruited within lymphoid infiltrates and activated by mature DC likely through TAA presentation, resulting in the prevention of effector T-cell activation, immune escape, and ultimately tumor progression. This study sheds new light on Treg physiology and validates CCR4/CCL22 and ICOS as therapeutic targets in breast tumors, which represent a major health problem.

Purpose: Although dendritic cells (DC) and T cells can infiltrate primary breast carcinoma, it remains unclear whether the immune response influences the clinical outcome.Experimental Design: T lymphocytes and DC infiltration within primary tumors was investigated in 152 patients with invasive nonmetastatic breast cancer. CD1a, CD3, CD68, CD123, CD207/Langerin, and CD208/DC-LAMP expression was assessed with semiquantitative immunohistochemical analysis. Expression of chemokines involved in DC migration (MIP-3a/CCL20, MIP-3b/CCL19, and 6Ckine/ CCL21) was also examined. The correlation between these markers and the characteristics of the tumors, as well as relapse-free and overall survival was analyzed. Significant prognostic parameters were then tested in a validation series.Results: Infiltration by immature CD207/Langerin ؉ DC was found in a third of the cancers and did not correlate with clinicopathological data. Presence of mature CD208/DC-LAMP ؉ DC (56%) and CD3 ؉ T cells (82%) strongly correlated with lymph node involvement and tumor grade. Among the chemokines analyzed, only the presence of MIP-3b/CCL19 in 57% of the tumors correlated with prolonged overall survival. CD123 ؉ plasmacytoid DC (pDC) infiltrated 13% of the primary tumors. Their presence was strongly associated with shorter overall survival (93% versus 58% at 60 months) and relapse-free survival (90% versus 37% at 60 months) and was found to be an independent prognostic factor for overall survival and relapse-free survival and confirmed in an independent validation series of 103 patients.Conclusions: Infiltration by pDC of primary localized breast tumor correlates with an adverse outcome, suggesting their contribution in the progression of breast cancer.

Infiltration and dysfunction of immune cells have been documented in many types of cancers. We previously reported that plasmacytoid dendritic cells (pDC) within primary breast tumors correlate with an unfavorable prognosis for patients. The role of pDC in cancer remains unclear but they have been shown to mediate immune tolerance in other pathophysiologic contexts. We postulated that pDC may interfere with antitumor immune response and favor tolerance in breast cancer. The present study was designed to decipher the mechanistic basis for the deleterious impact of pDC on the clinical outcome. Using fresh human breast tumor biopsies (N ¼ 60 patients), we observed through multiparametric flow cytometry increased tumor-associated (TA) pDC (TApDC) rates in aggressive breast tumors, i.e., those with high mitotic index and the so-called triple-negative breast tumors (TNBT). Furthermore, TApDC expressed a partially activated phenotype and produced very low amounts of IFN-a following toll-like receptor activation in vitro compared with patients' blood pDC. Within breast tumors, TApDC colocalized and strongly correlated with TA regulatory T cells (TATreg), especially in TNBT. Of most importance, the selective suppression of IFN-a production endowed TApDC with the unique capacity to sustain FoxP3 þ Treg expansion, a capacity that was reverted by the addition of exogenous IFN-a. These findings indicate that IFNa-deficient TApDC accumulating in aggressive tumors are involved in the expansion of TATreg in vivo, contributing to tumor immune tolerance and poor clinical outcome. Thus, targeting pDC to restore their IFN-a production may represent an attractive therapeutic strategy to overcome immune tolerance in breast cancer. Cancer Res; 72(20); 5188-97. Ó2012 AACR.

The recruitment of selected dendritic cell (DC) subtypes conditions the class of the immune response. Here we show that the migration of human plasmacytoid DCs (pDCs), the blood natural interferon ␣ -producing cells, is induced upon the collective action of inducible and constitutive chemokines. Despite expression of very high levels of CXCR3, pDCs do not respond efficiently to CXCR3 ligands. However, they migrate in response to the constitutive chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12 and CXCR3 ligands synergize with SDF-1/CXCL12 to induce pDC migration. This synergy reflects a sensitizing effect of CXCR3 ligands, which, independently of a gradient and chemoattraction, decrease by 20-50-fold the threshold of sensitivity to SDF-1/CXCL12. Thus, the ability of the constitutive chemokine SDF-1/CXCL12 to induce pDC recruitment might be controlled by CXCR3 ligands released during inflammation such as in virus infection. SDF-1/CXCL12 and the CXCR3 ligands Mig/CXCL9 and ITAC/CXCL1 display adjacent expression both in secondary lymphoid organs and in inflamed epithelium from virus-induced pathologic lesions. Because pDCs express both the lymph node homing molecule l -selectin and the cutaneous homing molecule cutaneous lymphocyte antigen, the cooperation between inducible CXCR3 ligands and constitutive SDF-1/CXCL12 may regulate recruitment of pDCs either in lymph nodes or at peripheral sites of inflammation.

In ovarian cancer, the immune system fails to eradicate established tumors partly due to the induction of immune tolerance within tumor microenvironment. In this study, we investigated the contribution of plasmacytoid dendritic cells (pDC) in the establishment of immune tolerance in a cohort of 44 ovarian cancer patients. In the tumor and malignant ascites, CD4 þ CD123 þ BDCA2 þ pDC were the most abundant dendritic cell subset; however, they were profoundly depleted in peripheral blood. The presence of pDC in primary ovarian cancer, but not ascites, was an independent prognostic factor associated with early relapse. Following chemotherapy, we observed a partial restoration of blood pDC levels in patients in complete remission. These findings show preferential recruitment of pDC into tumors where they express a partially mature phenotype that may reflect an in situ activation. Importantly, compared with pDC found in ascites or blood, tumor-associated pDC (TApDC) produced less IFN-a, TNF-a, IL-6, macrophage inflammatory protein-1b, and RANTES in response to toll-like receptor stimulation, and alterations in pDC functions were mainly mediated through tumor-derived TNF-a and TGF-b. Unlike ascites-derived pDC, TApDC induced IL-10 production from allogeneic naive CD4 þ T lymphocytes, suggesting the existence of a paracrine immunosuppressive loop. Taken together, our findings indicate that both local and systemic dysfunction of pDC play a critical role in the progression of ovarian cancer via induction of immune tolerance. Cancer Res; 71(16); 5423-34. Ó2011 AACR.

Recent studies in humans have highlighted the importance of a distinct cellular entity, the plasmacytoid dendritic cell (PDC). To identify genes for which expression is restricted to human PDCs, a cDNA subtraction technique was applied using cDNA from activated monocyte-derived DCs (MDDCs) as competitor. In the 650 sequences analyzed, 25% were for B-cell transcripts. We also found lymphoid-

Neutrophils are an essential part of the innate immune system. To study their importance, experimental studies often aim to deplete these cells, generally by injecting anti-Ly6G or anti-Gr1 antibodies. However, these approaches are only partially effective, transient or lack specificity. Here we report that neutrophils remaining after anti-Ly6G treatment are newly derived from the bone marrow, instead of depletion escapees. Mechanistically, newly generated, circulating neutrophils have lower Ly6G membrane expression, and consequently reduced targets for anti-Ly6G-mediated depletion. To overcome this limitation, we develop a double antibody-based depletion strategy that enhances neutrophil elimination by anti-Ly6G treatment. This approach achieves specific, durable and controlled reduction of neutrophils in vivo, and may be suitable for studying neutrophil function in experimental models.

Human breast tumors are infiltrated by memory CD4 þ T cells along with increased numbers of regulatory T