Phagocytes, Zombie Cells, and Macrophages

Susan "Doctor, can lysosomes also break down microbes that have invaded the body — back into basic units?"

Dr. Lee "Yes. Among immune cells, the very first line of defense — innate immunity — consists of phagocytes (Murphy & Weaver, 2017). Dendritic cells and macrophages are the classic examples (Underhill & Goodridge, 2012). They engulf invading microbes to defend the body, and the engulfed microbes are then broken down to basic units by the lysosome's hydrolases."

Grace "That must be why people say to fast when you're sick. Dogs and animals in nature stop eating when they're ill."

Dr. Lee "Exactly. When you don't eat, immune cells become hungry and patrol the body more aggressively, hunting down microbes (Figure 3-9). Experiments show that a single macrophage can engulf up to 12 other cells. So even macrophages stop hunting when they're full. Notably, eating saturated fat slows macrophage activity."