An update on the Tenebrio molitor immune system

Infections caused by pathogenic microorganisms represent a crucial challenge for the host's health and well-being, since they are a threat to its survival. During the species evolution, organisms developed a protective system against their microscopic disease-causing adversaries, which is a notable and highly valuable trait in the adaptation of living beings. The immune response is responsible for self- and non-self-recognition, an elemental step in establishing protective mechanisms. In invertebrates, innate immunity orchestrates the attack against pathogens. Insect immunity is composed of cellular responses mediated by hemocytes, as well as humoral effectors, which are soluble molecules with high antimicrobial potential. Notably, many of these components have a high degree of structural and functional similarity to mammalian immune effectors. Humoral effectors and hemocytes act synergistically for the recognition and control of bacteria, fungi, viruses, and parasites. The activation of signaling pathways is the first step in pathogen recognition, and in insects, both the Toll and immune deficiency pathways are the main ones that trigger effector responses, including antimicrobial peptides, opsonins, lysozymes, and metalloproteinase inhibitors, among others. Here, we summarize the main findings on Tenebrio molitor immunity and highlight relevant gaps in current knowledge of this beetle's biology.