COVER Lipid nanoparticles (spheres) use antibodies against the CD5 protein (antibodies, blue; CD5, red) to specifically target T cells while inside the bloodstream and tissues. The nanoparticles deliver mRNA to T cells, reprogramming them in vivo to transiently express chimeric antigen receptors (gold) that target pathogenic cardiac fibroblasts. In vivo–engineered T cells mitigate cardiac fibrosis and improve heart function in a mouse model. See pages 23 and 91.

Illustration: C. Bickel/Science

ONLINE COVER To promote and maintain neural connectivity, endosomes carry survival signals to the nuclei of nerve cells. But how do endosomes find their way over the long distances from the synapse (the space between nerve cells) to the nucleus? Using microfluidic devices and mice, Scaramuzzino et al. found that the endosomes (blue spheres), which are tethered to molecular motors walking along the microtubule network (green rods), carry a calcium-sensing molecule on their surface that provides an internal navigation system to guide them toward the nucleus (orange globe). This work may increase understanding of several neurodegenerative diseases.

ONLINE COVER Trail Markers for Tissue Macrophages. This month's cover illustration depicts a trail marker post in a desert landscape that provides a guide to deciphering the diversity among mouse and human tissue-resident macrophages. The trio of phenotypes (TLF⁺, CCR2⁺ and MHC-II⁺) listed on the post represent three conserved macrophage subsets defined by Dick et al. These subsets share common core gene signatures and life cycles across 17 different mouse tissues.

ONLINE COVER Takeoff and Landings. The ability for aerial robots to take off and land on a variety of irregular surfaces will broaden the range of environments where these robots could be deployed. Influenced by how birds take off, land, and grasp, Roderick et al. have developed a bird-inspired grasping system called Stereotyped Nature-inspired Aerial Grasper (SNAG). The researchers integrated SNAG into a quadcopter to demonstrate perching on tree branches of different sizes, orientations, and surface conditions. This month's cover is a photograph of SNAG on a quadcopter perched on a branch.

ONLINE COVER This week, Kim et al. report that zinc metabolically reprograms monocytes and macrophages to promote inflammation in rheumatoid arthritis. The image is an illustration of a coronal section through a rheumatoid arthritis–afflicted knee joint.

ONLINE COVER Heating Up Tumors. This image shows co-expression (yellow) of the oncoprotein Tribbles homolog 3 (TRIB3, green) and the acetyltransferase P300 (red) in tumor tissue from a patient with colorectal cancer. Nuclei are shown in blue. Converting immune "cold" tumors that have poor T cell infiltration to highly infiltrated, immune "hot" tumors is a promising strategy to improve outcomes for colorectal cancer. Shang et al. demonstrated that TRIB3 inhibited CD8⁺ T cell infiltration into colorectal tumors by reducing CXCL10 production. P300-mediated acetylation stabilized TRIB3 protein, which could be reversed by treating colorectal cancer tumor-bearing mice with a P300 inhibitor. Treatment increased CD8⁺ T cell infiltration into tumors and sensitized them to immune checkpoint blockade, suggesting that TRIB3 may be a useful target for colorectal cancer.