Single-walled carbon nanotubes (CNTs) emit heat when they absorb energy from near-infrared (NIR) light. Tissue is relatively transparent to NIR, which suggests that targeting CNTs to tumor cells, followed by noninvasive exposure to NIR light, will ablate tumors within the range of NIR. In this study, we demonstrate the specific binding of antibody-coupled CNTs to tumor cells in vitro , followed by their highly specific ablation with NIR light. Biotinylated polar lipids were used to prepare stable, biocompatible, noncytotoxic CNT dispersions that were then attached to one of two different neutralite avidin-derivatized mAbs directed against either human CD22 or CD25. CD22 ⁺ CD25 ⁻ Daudi cells bound only CNTs coupled to the anti-CD22 mAb; CD22 ⁻ CD25 ⁺ activated peripheral blood mononuclear cells bound only to the CNTs coupled to the anti-CD25 mAb. Most importantly, only the specifically targeted cells were killed after exposure to NIR light.

Radiation therapy (RT), a major modality for treating localized tumors, can induce tumor regression outside the radiation field through an abscopal effect that is thought to involve the immune system. Our studies were designed to understand the early immunological effects of RT in the tumor microenvironment using several syngeneic mouse tumor models. We observed that RT induced sterile inflammation with a rapid and transient infiltration of CD11b⁺Gr-1^high+ neutrophils into the tumors. RT-recruited tumor-associated neutrophils (RT-Ns) exhibited an increased production of reactive oxygen species and induced apoptosis of tumor cells. Tumor infiltration of RT-Ns resulted in sterile inflammation and, eventually, the activation of tumor-specific cytotoxic T cells, their recruitment into the tumor site, and tumor regression. Finally, the concurrent administration of granulocyte colony-stimulating factor (G-CSF) enhanced RT-mediated antitumor activity by activating RT-Ns. Our results suggest that the combination of RT and G-CSF should be further evaluated in preclinical and clinical settings. Significance The role of tumor-associated neutrophils (TANs) in cancer progression versus regression remains controversial. TANs are known to have dichotomous antitumor (N1) and protumor (N2) phenotypes depending on the tumor microenvironment. Past studies have demonstrated that TANs are polarized from an N2 to an N1 phenotype in the absence of TGF-β; N1 TANs are not induced in the absence of IFN-β. Our study demonstrates that radiation therapy (RT) and, especially, the combination of RT and granulocyte colony-stimulating factor (G-CSF) induces the polarization of N1 TANs [RT-recruited TANs (RT-Ns)]. Reactive oxygen species produced by RT-Ns damage tumor tissues in a manner analogous to the manner in which neutrophils affect damaged normal tissues. Our studies suggest that enhancing the activity of TANs during RT improves its antitumor activity.

In 1997, a chimeric anti-CD20 monoclonal antibody (mAb) (Rituxan) was approved for the treatment of low-grade/follicular B-cell lymphoma. Rituxan has a long half-life and low immunogenicity, and it mediates effector function. Rituxan induces apoptosis in some tumor cell lines in vitro. Previous studies with mAbs that react with neoplastic B cells have demonstrated that homodimers of immunoglobulin G ([IgG]₂) often inhibit cell growth more effectively than their monomeric (IgG)₁counterparts. In this study, the ability of IgG or F(ab′)₂ homodimers vs monomers of Rituxan were compared for their ability to inhibit the growth of several different B-lymphoma cell lines in vitro. It was found that homodimers of Rituxan had superior antigrowth activity in vitro and that F(ab′)₂ homodimers were the most active. Homodimers, but not monomers, of Rituxan induced both apoptosis and necrosis of several B-cell lymphoma lines in vitro; the inhibition of cell growth was not dependent upon the presence of Fc receptors or upon 10-fold or greater differences in the density of CD20 on the target cells. Rituxan homodimers, compared with monomers, also rendered drug-resistant CD20⁺ B-lymphoma cells more sensitive to chemotherapeutic agents and synergized with an anti-CD22 immunotoxin in vitro.

IFN-γ is a major cytokine that is critical for host resistance to a broad range of intracellular pathogens. Production of IFN-γ by natural killer and T cells is initiated by the recognition of pathogens by Toll-like receptors (TLRs). In an experimental model of toxoplasmosis, we have identified the presence of a nonlymphoid source of IFN-γ that was particularly evident in the absence of TLR-mediated recognition ofToxoplasma gondii. Genetically altered mice lacking all lymphoid cells due to deficiencies in Recombination Activating Gene 2 and IL-2Rγ_cgenes also produced IFN-γ in response to the protozoan parasite. Flow-cytometry and morphological examinations of non-NK/non-T IFN-γ⁺cells identified neutrophils as the cell type capable of producing IFN-γ. Selective elimination of neutrophils in TLR11^−/−mice infected with the parasite resulted in acute susceptibility similar to that observed in IFN-γ–deficient mice. Similarly,Salmonella typhimuriuminfection of TLR-deficient mice induces the appearance of IFN-γ⁺neutrophils. Thus, neutrophils are a crucial source for IFN-γ that is required for TLR-independent host protection against intracellular pathogens.