This image shows histologic images of the colon of wildtype (top) and Cyba nmf333 (bottom) mice. The compromised dense mucus layer in Cyba nmf333 mice facilitates penetration of microbiota into crypts, leading to direct contact of bacteria with the epithelium. Cyba nmf333 mice have a missense mutation in Ncf1 (p22phox) which renders NADPH oxidases Nox1-3 inactive while preserving Nox4 activity. Image courtesy of Dr. Ulla Knaus and Dr. Dimitri Scholz, Conway Institute, School of Medicine, University College Dublin. For further information, please see the article in this issue, pages 1316–1326.

This diagram illustrates the mechanisms by which neutrophils are recruited and activated during respiratory syncytial virus (RSV) infection. RSV induces the production of neutrophil chemoattractants by stromal cells in a MYD88/TRIF dependent manner, driving neutrophil recruitment to the lungs. Meanwhile, alveolar macrophages produce type I interferons in a MAVS dependent manner inducing a pro-inflammatory cascade in the lungs. The recruited neutrophils become activated upon encountering this pro-inflammatory lung environment. Image courtesy of Freja Kirsebom and Cecilia Johansson, Imperial College London, created using BioRender. For further information, please see the article in this issue, pages 1244–1255.

Intestinal epithelial cells showing F-actin rich cytoplasmic extensions in cells migrating to heal a wound. Phosphorylation and activation of focal adhesion kinase (FAK) in concert with integrins and associated proteins regulates cell movement and wound repair. The image shows F-actin(red), pFAK Y861 (green) and nuclei (blue) in migrating epithelial cells.

Corneal scarring can lead to irreversible visual impairment. Here, multiphoton second harmonic generation (SHG) microscopy shows immunopathologic corneal fibrosis resulting from Herpes Simplex Virus (HSV)-1 infection through forward (magenta) and reverse (cyan)collagen SHG signals. Royer et al. found that prophylactic immunity elicited from a live-attenuated HSV-1 vaccine provides antibody-mediated protection against HSV-1 pathogenesis and prevents corneal scarring following ocular challenge in mice.

This image shows a high density of lymphoid structures in Peyer’s patches of the human ileum from an 18 month old pediatric organ donor. Frozen intestinal tissues were stained for expression of CD4 (green), CD8 (blue), and CD45RA (red) for distinguishing T cells and B cell follicles, and DAPI (cyan) to visualize nucleated cells.

Shown on the cover is an immunofl uorescent image of lung parenchymal tissue from a Trefoil factor 2/td-Tomato knock-in reporter mouse 4 days postinfection with the gastrointestinal nematode parasite N. brasiliensis. TFF2 expressing alveolar macrophages and epithelial cells are shown in red, and alveoli and small airway epithelial cells in blue. Note the position of the large TFF2 positive mononuclear cells positioned in the alveolar space that accumulate at the nidus of injury caused by the parasite infection. Further evidence in the current manuscript supports a role for TFF2 in epithelial cell repair following lung injury. For further information see article in this issue, page 68. Image Courtesy of De’Broski R. Herbert, University of Pennsylvania School of Veterinary Medicine.