The antibodies found in mucus, saliva, and tears are primarily immunoglobulin A (IgA).
IgA plays a crucial role in the immune function of mucosal areas. It helps to prevent pathogens from attaching to and penetrating epithelial cells. When you encounter germs or allergens, IgA is produced in larger amounts and secreted into these fluids to neutralize threats before they can cause harm.
In addition to IgA, minor amounts of other antibodies like IgG and IgM can also be present in these secretions, but IgA is the dominant antibody type. This makes it essential for the first line of defense in protecting mucosal surfaces, such as those in the respiratory and digestive tracts.