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How do protective antibodies in mucus help defend the respiratory tract?

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Immune stimulation by activated helper T cells — immune system Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, T_H1 and T_H2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.

Protective antibodies, specifically IgA, play a critical role in defending the respiratory tract by preventing pathogens from invading the body's tissues.1

Unlike other immune mechanisms that rely on complement proteins, IgA functions primarily by binding to microbes on the surface of the mucous membrane. By attaching to these pathogens, the antibodies block them from entering or attaching to the cells that line the respiratory tract. Once the microbes are bound by IgA, they are effectively trapped within the mucus and are subsequently cleared from the body through the sweeping, upward motion of cilia, which propel the mucus and trapped particles out of the throat and nose. Additionally, IgA may assist in directing certain types of cell-mediated killing to further neutralize potential threats.12