Final answer:
Local IgA antibody prevents infection of the upper respiratory tract by binding to pathogens in secretions like mucus to neutralize them. This response protects mucosal surfaces and is a key aspect of the body's primary immune defense against airborne pathogens.
Step-by-step explanation:
The local IgA antibody plays a crucial role in the mucosal immune response by acting as a first line of defense against pathogens attempting to enter the body through mucosal surfaces. Specifically, option A, which states that local IgA prevents infection of the upper respiratory tract, is correct. IgA antibodies are present in mucus and other secretions and can bind to pathogens such as viruses and bacteria to neutralize them. This process inhibits the pathogens from adhering to cellular receptors and initiating an infection. It's important to note that secretory IgA not only prevents upper respiratory tract infections but also provides protection for mucosal surfaces throughout the body, including the lower respiratory tract, although the question asked about upper respiratory tract explicitly.
The upper respiratory system is closely watched by mucosa-associated lymphoid tissue (MALT) and receives additional support from secreted antibodies like IgA, along with other defenses such as lysozyme and antimicrobial peptides. These defenses work together to protect the body from infection. In contrast, the recovery from lung infection relies on the overall immune response, including various immune cells and other types of antibodies, not solely on IgA.