The body’s immune system utilizes oxygen’s powerful oxidizing potential on pathogens in another remarkable way.
When a pathogen infects the body, the body recognizes this invasion and sends a host of warrior cells to attack and destroy this unwanted guest. We call these soldiers “white blood cells” but the scientific term is “phagocyte”.
A white blood cell (phagocyte) in the blood stream surrounded by red blood cells.
When a pathogen is in close proximity to a phagocyte, some sort of signal, (the nature of which is still not clearly understood,) triggers the phagocyte digestion (ingestion) process. Ingestion involves the encircling of the target pathogen with the phagocytic membrane so that the pathogen is actually taken inside the cytoplasm of the phagocyte. It is engulfed in a membrane vesicle called a phagosome.
This process requires ATP (energy created by “oxygen”). Contact between a pathogen and a phagocyte also changes the phagocyte's metabolism from an aerobic respiratory process to anaerobic fermentative process, with lactic acid being the final end product. This increase in lactic acid in the phagocyte lowers the pH of the cytoplasm, including the phagolysosome, and this enhances the activity of many of the degradative enzymes present.
The phagosome, containing the microorganism, migrates into the cytoplasm and soon collides with a series of lysosomes and forms a phagolysosome. When the membranes of the phagosome and lysosome meet, the contents of the lysosome explosively discharge, releasing a large number of toxic reactive oxygen macromolecules, as well as other compounds, into the
phagosome. The killing processes inside the phagolysosome are confined to the organelle of the phagolysosome, and this protects the cytoplasm of the phagocyte from these toxic activities.
A phagocyte attacks pathogens in the blood stream.
Several minutes after phagolysosome formation, the first detectable effect on the microorganism is that it loses its ability to reproduce. Inhibiting macromolecular synthesis occurs sometime later and most pathogenic organisms are dead 10 to 30 minutes after ingestion.