Is gastric juice considered to be a second line of defense?

Gastric juice is not typically classified as a second line of defense; rather, it is part of the body's first line of defense against pathogens. It contains hydrochloric acid and digestive enzymes that help to kill harmful microorganisms ingested with food. This acidic environment plays a crucial role in preventing infections in the gastrointestinal tract. The second line of defense generally refers to immune responses, such as inflammation and the action of white blood cells, which respond to pathogens that bypass the first line of defense.