On the cover: Pseudomonas aeruginosa is a Gram-negative bacteria and common pathogen that infects the lungs of patients with cystic fibrosis. Lung macrophages are the first line of defense in the airway innate immune response to pathogens. The scanning electron microscopy image (pseudocolored) shows P. aeruginosa (purple) being enveloped and phagocytized by cell surface ruffles of a lung macrophage (blue). Image credit: D. A. Armstrong, L. Howard, and A. Zhang (2019). Armstrong, D. A., M. K. Lee, H. F. Hazlett, J. A. Dessaint, D. L. Mellinger, D. S. Aridgides, G. M. Hendricks, M. A. K. Abdalla, B. C. Christensen and A. Ashare. 2020. Extracellular vesicles from Pseudomonas aeruginosa suppress MHC-related molecules in human lung macrophages. ImmunoHorizons 4: 508–519.