In Greek, the word “macrophage” means “big eaters,” which is exactly what macrophages do. They are notably large cells whose job, as part of the innate immune response, is to engulf and digest cellular debris and invasive pathogens. They also stimulate other components of the immune system.
In this scanning electron micrograph from Nicole Ottawa and Oliver Meckes at eye of science, a macrophage (colored pale brown) interacts with Borrelia cells (colored blue), a spirochete bacteria that causes Lyme disease. The surface of Borrelia contains a strong antigen capable of provoking an immune response. The bacterium compensates by hiding in places where it’s less likely to be found by immune cells like macrophages, such as the central nervous system.