Inhibitory receptors on immune cells are pivotal regulators of immune escape in cancer. Among these inhibitory receptors, CTLA-4 (targeted clinically by ipilimumab) serves as a dominant off-switch while other receptors such as PD-1 and LAG-3 seem to serve more subtle rheostat functions. However, the extent of synergy and cooperative interactions between inhibitory pathways in cancer remain largely unexplored. Here we reveal extensive co-expression of PD-1 and LAG-3 on tumor-infiltrating CD4+ and CD8+ T cells in three distinct transplantable tumors. Dual anti-LAG-3/anti-PD-1 antibody treatment cured most mice of established tumors that were largely resistant to single antibody treatment. Despite minimal immunopathological sequelae in PD-1 and LAG-3 single knockout mice, dual knockout mice abrogated self-tolerance with resultant autoimmune infiltrates in multiple organs, leading to eventual lethality. However, Lag3−/−Pdcd1−/− mice demonstrated markedly increased survival from and clearance of multiple transplantable tumors. Together, these results define a strong synergy between the PD-1 and LAG-3 inhibitory pathways in tolerance to both self and tumor antigens. Additionally, they argue strongly that dual blockade of these molecules represents a promising combinatorial strategy for cancer.

Novel nanomaterials for bioassay applications represent a rapidly progressing field of nanotechnology and nanobiotechnology. Here, we present an exploration of single-walled carbon nanotubes as a platform for investigating surface-protein and proteinprotein binding and developing highly specific electronic biomolecule detectors. Nonspecific binding on nanotubes, a phenomenon found with a wide range of proteins, is overcome by immobilization of polyethylene oxide chains. A general approach is then advanced to enable the selective recognition and binding of target proteins by conjugation of their specific receptors to polyethylene oxide-functionalized nanotubes. This scheme, combined with the sensitivity of nanotube electronic devices, enables highly specific electronic sensors for detecting clinically important biomolecules such as antibodies associated with human autoimmune diseases. R ecent years have witnessed significant interest in biological applications of novel inorganic nanomaterials such as nanocrystals (1, 2), nanowires (3), and nanotubes (4, 5) with the motivation to create new types of analytical tools for life science and biotechnology. Single-walled carbon nanotubes (SWNTs) are interesting molecular wires (diameter Ϸ1-2 nm) with unique electronic properties that have been spotlighted for future solid-state nanoelectronics (6, 7). Bridging nanotubes with biological systems, however, is a relatively unexplored area, with the exception of a few reports on nanotube probe tips for biological imaging (4), nonspecific binding (NSB) of proteins (8-10), functionalization chemistry for bioimmobilization on nanotube sidewalls (5), and one study on biocompatibility (11).Previously, we and others have shown that the electrical conductance of a nanotube is highly sensitive to its environment and varies significantly with changes in electrostatic charges and surface adsorption of various molecules (12)(13)(14). This research has hinted at possible SWNT-based miniature sensors for detecting biological molecules in fluids. Here, we systematically explore how nanotubes interact with and respond to various proteins in solution, how chemical functionalization can be used to tailor these interactions, and how the resulting understanding enables highly selective nanotube sensors for the electronic detection of proteins. Using atomic force microscopy (AFM) and quartz crystal microbalance (QCM) and electronic transport measurements, we first reveal that proteins in general exhibit a high degree of NSB on nanotubes, a phenomenon undesirable for potential biosensors. We then demonstrate a functionalization scheme involving irreversible adsorption of Tween 20 or triblock copolymer chains on nanotubes to prevent this general NSB, while at the same time enabling the binding of specific proteins of interest that can be detected electronically without the need for labeling. Further, we demonstrate specific detection of mAbs to the human autoantigen U1A, a prototype target of the autoimmune response in patients with systemic lupu...