A Comprehensive review of humoral immune defense in the silkworm, Bombyx mori: Mechanistic insights and responses to microbial pathogens

The silkworm Bombyx mori L. is an economically valuable insect and an excellent model for investigating insect immunity. Its robust innate immune system shields it from numerous pathogens, such as viruses, bacteria, fungi, and microsporidia. The innate immune system comprises two overlapping mechanisms, known as the humoral and cellular immune systems. It depends on recognition receptors to distinguish the pathogen-associated molecular patterns (PAMPs), which stimulate numerous immunoresponsive pathways comprising JAK- STAT, Toll, Imd, and RNA interference. This review examines the humoral immune response, highlighting its critical components, including antimicrobial peptides, phenoloxidase (PO), pattern recognition receptors (PRRs), signaling pathways, and humoral effectors molecules. These processes synergistically counter and eradicate infectious microbes, thus aiding silkworms' immune defense. Expanding the understanding of humoral immune responses is key for comprehending molecular bases of innate immunity and essential immune elements distributed among silkworms and other invertebrates. Moreover, it could offer significant prospects for optimizing silk production methods, developing strategies for preventing infections affecting silk yield, and offering a theoretical framework for the future investigation of insect immunology.