Immunosuppression is a known risk factor for B-cell non-Hodgkin lymphoma (NHL), yet mechanisms of tumor-associated immunosuppression remain to be fully characterized. We examined the immunophenotype of 40 NHL patients and 27 age-matched healthy volunteers to better understand systemic immune suppression. NHL peripheral blood mononuclear cells had significantly decreased interferon-␥ production and proliferation. This suppression was not the result of regulatory T cells, interleukin-6 or interleukin-10, as these factors were not different between NHL and healthy volunteers (controls). We were able to restore T-cell proliferation by removing NHL monocytes, suggesting that these monocytes are suppressive. This suppression was mediated in part through arginine metabolism as exogenous arginine supplementation partially overcame monocytes' suppression of T-cell proliferation in vitro and NHL patients had elevated arginase I in their plasma. NHL monocytes had impaired STAT1 phosphorylation and interferon-␣ production to CpG stimulation and a dendritic cell differentia- IntroductionSystemic immune suppression is often seen in cancer patients and is thought to contribute to patient morbidity via tumor-mediated immune evasion. Indeed, patients with compromised immune systems, such as those with HIV infection, or on immunosuppressive medications are at increased risk of developing non-Hodgkin lymphoma (NHL). 1,2 Polymorphisms in host germline immune genes also have been associated with risk of developing NHL 3 as well as survival in NHL patients. 4 Conversely, a small percentage of patients with indolent NHL have spontaneous regression of their disease without any treatment, 5 possibly linked to a host antitumor immune response. The presence of host immune cells in the tumor microenvironment has also been correlated with treatment outcome and survival. [6][7][8][9] Of note, reduction in absolute count of circulating lymphocytes has been identified as a poor prognostic factor for overall survival in newly diagnosed NHL 10,11 as well as a predictor of poor treatment response. 9,12,13 Although evidence for the role of immune suppression in tumor establishment and pathogenesis is unquestionable, the mechanisms and the cellular phenotype of systemic immune suppression in NHL patients remain to be fully characterized.In this study, we investigated the qualitative and quantitative systemic immune suppression in B-cell NHL. We found circulating mononuclear cells had suppressed interferon-␥ (IFN-␥) recall response and proliferative capacity. These suppressed functions were mediated by circulating monocytes and partly mediated via arginine metabolism. These monocytes also had other impaired adaptive immune response including a decreased capacity to generate mature dendritic cells. In addition, the innate immune response of these monocytes to CpG stimulation was impaired as measured by intracellular STAT1 phosphorylation and interferonalpha (IFN-␣) production. These multifactorial suppressive functions of monocytes in NHL were corre...

Patients with glioblastoma (GBM) exhibit profound systemic immune defects that affect the success of conventional and immune-based treatments. A better understanding of the contribution of the tumor and/or therapy on systemic immune suppression is necessary for improved therapies, to monitor negative effects of novel treatments, to improve patient outcomes, and to increase understanding of this complex system. To characterize the immune profile of GBM patients, we phenotyped peripheral blood and compared these to normal donors. In doing so, we identified changes in systemic immunity associated with both the tumor and dexamethasone treated tumor bearing patients. In particular, dexamethasone exacerbated tumor associated lymphopenia primarily in the T cell compartment. We have also identified unique tumor and dexamethasone dependent altered monocyte phenotypes. The major population of altered monocytes (CD14(+)HLA-DR(lo/neg)) had a phenotype distinct from classical myeloid suppressor cells. These cells inhibited T cell proliferation, were unable to fully differentiate into mature dendritic cells, were associated with dexamethasone-mediated changes in CCL2 levels, and could be re-created in vitro using tumor supernatants. We provide evidence that tumors express high levels of CCL2, can contain high numbers of CD14(+) cells, that tumor supernatants can transform CD14(+)HLA-DR(+) cells into CD14(+)HLA-DR(lo/neg) immune suppressors, and that dexamethasone reduces CCL2 in vitro and is correlated with reduction of CCL2 in vivo. Consequently, we have developed a model for tumor mediated systemic immune suppression via recruitment and transformation of CD14(+) cells.