Immunoglobulin A (IgA) is an antibody produced by the immune system that plays a key role in protecting the mucosal surfaces of the body, such as the respiratory and gastrointestinal tracts, saliva and tears. It provides a first line of defense against pathogens, neutralizing toxins and preventing their attachment and penetration into tissues. This type of antibody is of particular importance in maintaining the balance in the gut microbiota and preventing infections in the respiratory tract. IgA is also transmitted to newborns through breast milk, providing them with passive immunity. Measuring IgA levels in the blood can be useful for diagnosing conditions related to the immune system and for monitoring a healthy balance in the body. Knowing the role of IgA is essential to understanding their function in the immune system and maintaining the health of the body.