Michele Swanson, Ph.D., Professor, Department of Microbiology and Immunology, University of Michigan Medical School

White blood cells like this macrophage protect our lungs from infection by efficiently ingesting, killing, and digesting most microbes that we inhale. However, the bacterium known as Legionalla pneumophila (stained purple) survives and even replicates within these cells. The pathogen's name emphasizes its discovery after a fatal outbreak of pneumonia at a gathering of Legionnaires in Philadelphia in the USA bicentennial year 1976: "Legionalla" from Legionnaire; "pnuemo" meaning lung; "phila" meaning love.