CD4+ Natural Regulatory T Cells Prevent Experimental Cerebral Malaria via CTLA-4 When Expanded In Vivo

Studies in malaria patients indicate that higher frequencies of peripheral blood CD4+ Foxp3+ CD25+ regulatory T (Treg) cells correlate with increased blood parasitemia. This observation implies that Treg cells impair pathogen clearance and thus may be detrimental to the host during infection. In C57BL/6 mice infected with Plasmodium berghei ANKA, depletion of Foxp3+ cells did not improve parasite control or disease outcome. In contrast, elevating frequencies of natural Treg cells in vivo using IL-2/anti-IL-2 complexes resulted in complete protection against severe disease. This protection was entirely dependent upon Foxp3+ cells and resulted in lower parasite biomass, impaired antigen-specific CD4+ T and CD8+ T cell responses that would normally promote parasite tissue sequestration in this model, and reduced recruitment of conventional T cells to the brain. Furthermore, Foxp3+ cell-mediated protection was dependent upon CTLA-4 but not IL-10. These data show that T cell-mediated parasite tissue sequestration can be reduced by regulatory T cells in a mouse model of malaria, thereby limiting malaria-induced immune pathology

Effects of stimulating interleukin -2/anti- interleukin -2 antibody complexes on renal cell carcinoma

BACKGROUND: Current therapies for advanced renal cell carcinoma (RCC) have low cure rates or significant side effects. It has been reported that complexes composed of interleukin (IL)-2 and stimulating anti-IL-2 antibody (IL-2C) suppress malignant melanoma growth. We investigated whether it could have similar effects on RCC. METHODS: A syngeneic RCC model was established by subcutaneously injecting RENCA cells into BALB/c mice, which were administered IL-2C or phosphate-buffered saline every other day for 4 weeks. RCC size was measured serially, and its weight was assessed 4 weeks after RENCA injection. Immune cell infiltration into RCC lesions and spleen was assessed by flow cytometry and immunohistochemistry. RESULTS: IL-2C treatment increased the numbers of CD8(+) memory T and natural killer (NK) cells in healthy BALB/c mice (P < 0.01). In the spleen of RCC mice, IL-2C treatment also increased the number of CD8(+) memory T, NK cells, and macrophages as compared to PBS-treated controls (P < 0.01). The number of interferon-γ- and IL-10-producing splenocytes increased and decreased, respectively after 4 weeks in the IL-2C-treated mice (P < 0.01). Tumor-infiltrating immune cells including CD4(+) T, CD8(+) T, NK cells as well as macrophages were increased in IL-2C-treated mice than controls (P < 0.05). Pulmonary edema, the most serious side effect of IL-2 therapy, was not exacerbated by IL-2C treatment. However, IL-2C had insignificant inhibitory effect on RCC growth (P = 0.1756). CONCLUSIONS: IL-2C enhanced immune response without significant side effects; however, this activity was not sufficient to inhibit RCC growth in a syngeneic, murine model

G-CSF/anti-G-CSF antibody complexes drive the potent recovery and expansion of CD11b+Gr-1+ myeloid cells without compromising CD8+ T cell immune responses

BACKGROUND: Administration of recombinant G-CSF following cytoreductive therapy enhances the recovery of myeloid cells, minimizing the risk of opportunistic infection. Free G-CSF, however, is expensive, exhibits a short half-life, and has poor biological activity in vivo. METHODS: We evaluated whether the biological activity of G-CSF could be improved by pre-association with anti-G-CSF mAb prior to injection into mice. RESULTS: We find that the efficacy of G-CSF therapy can be enhanced more than 100-fold by pre-association of G-CSF with an anti-G-CSF monoclonal antibody (mAb). Compared with G-CSF alone, administration of G-CSF/anti-G-CSF mAb complexes induced the potent expansion of CD11b(+)Gr-1(+) myeloid cells in mice with or without concomitant cytoreductive treatment including radiation or chemotherapy. Despite driving the dramatic expansion of myeloid cells, in vivo antigen-specific CD8(+) T cell immune responses were not compromised. Furthermore, injection of G-CSF/anti-G-CSF mAb complexes heightened protective immunity to bacterial infection. As a measure of clinical value, we also found that antibody complexes improved G-CSF biological activity much more significantly than pegylation. CONCLUSIONS: Our findings provide the first evidence that antibody cytokine complexes can effectively expand myeloid cells, and furthermore, that G-CSF/anti-G-CSF mAb complexes may provide an improved method for the administration of recombinant G-CSF