Protective Responses in Invertebrates

In metazoans, foreign molecules from bacteria or fungi, pathogens, parasites, or chemicals can generate serious stress stimuli, activating multiple humoral and cellular responses of innate immunity, which is the first line of defense for organisms. In invertebrates, the presence of an ancestral defense, based on a mix of combined immune-neuroendocrine responses, generates an efficient repertoire of reactions. Here we propose a summary of the protective events activated according to the cellular needs, the type of involved tissue/organ, or the specific lifetime, focusing on emerging concepts regarding solutions commonly utilized by immunocytes. A new player in various protective responses is “functional amyloidogenesis,” which is a basic event involved not only in melanin synthesis but also in detoxification processes against the overproduction of reactive oxygen species.