**4. Conclusions and perspectives**

We have reviewed some host molecules and their effects on the parasite. It is interesting to note how many distinct molecules produced along with the immune response (cytokines, pro or anti-inflammatory) or regularly produced by the endocrine system (such as sexual hormones) may interfere with parasites' development and fecundity. The study of molecular targets of this signaling is relevant to understanding how the evolution prepares the parasite's genome to respond and adapt to different signals from the environment and the hosts.

These biological models are exciting for system biology sciences and drug and vaccines discoveries; however, for a better understanding, functional genomic approaches must be improved to be applied in platyhelminths models to clarify the contribution of the signaling elements in the transduction and regulation of parasites' biological process.

As technologies have been developed and adapted, much information will be obtained from these particularly complex and challenging biological models. As information increases, new solutions for combating parasitic diseases will be elaborated and applied.
