What is the first step in the process of phagocytosis?

The first step in phagocytosis is the binding of the bacterium to the phagocytic cell. This process begins when a phagocyte, such as a macrophage or neutrophil, recognizes and attaches to pathogens through specific receptors on its surface. These receptors can recognize pathogen-associated molecular patterns (PAMPs) on the bacterial surface. Once the bacterium is bound, the phagocyte can then extend its membrane around the bacterium, leading to the formation of a phagosome.

This initial step is critical because it ensures that the phagocyte can specifically target and recognize harmful pathogens, setting the stage for the subsequent steps of phagocytosis, such as membrane invagination, fusion with lysosomes, and ultimately digestion of the engulfed material. Understanding this sequence is essential for grasping how the immune system responds to infections.