The class of antibodies produced predominantly against ingested antigens, found in body secretions such as saliva, sweat, or tears, and functioning to prevent attachment of viruses and bacteria to epithelial surfaces.免疫球蛋白A：对抗摄取抗原的主要抗体类，存在于身体分泌物（如唾液、汗液或眼泪）中，阻止病毒和细菌附着在上皮层