In complex multi-organ animals cells can migrate between distant tissues. This trans-organ migration is commonly used to distribute cells trough the body. This occurs, for example, when cell precursors are sent to target tissues to repopulate organs and maintain body homeostasis. This type of motility is also important for leukocytes, immune cells that upon infection migrate between organs to perform and coordinate adaptive immune responses. Trans-organ migration is also observed in pathological situations such as autoimmune diseases and cancer metastasis, highlighting the relevance and therapeutic potential of this function. The general objective of this proposal is to understand the mechanisms that make cells efficient in migration between distant organs. This proposal is focused in the study of leukocytes, immune cells that promptly colonize secondary tissues to ensure adaptive immune protection. Adaptive immunity starts by antigen recognition at the periphery of the body. This function is performed by dendritic cells (DCs), leukocytes that randomly scan tissues searching for harmful particles. After encountering with a pathogenic element such as bacterial products, DCs change their motile properties. They transit from a random migration to a more persistent and directional mode of locomotion. This change in motility is accompanied by chemokine guidance that drives DCs to lymphatic vessels, the pathway to lymph nodes. To enter the lymphatics DCs deform and expand preexisting portals localized at the surface of the vessels. Once inside, they get exposed to a flat shaped environment. At the end of their journey, DCs reach the draining lymph node, exit the lymphatics and then migrate towards the center of this secondary organ to encounter and activate cognate naïve T lymphocytes (TLs). After activation by DCs, TLs proliferate and exit the lymph node. They enter into blood vessels and home to the inflamed tissue where they perform the effector function of the adaptive immune system. Migration and colonization of a secondary tissue by DCs and TLs is extremely efficient, taking place in only few hours. However, the cellular machinery used by these leukocytes to migrate between distant organs remains elusive. The aim of this project is to take advantage of the professional capacity of leukocytes to colonize secondary tissues to decipher the cellular requirements that facilitate migration of cells between distant organs. I propose a multidisciplinary project that combines micro-fabrication, cell biology and immunology to identify cellular mechanisms that naturally evolved in immune cells to facilitate exchange of cells between tissues. Using novel in vitro micro-fabricated tools I will identify molecules that control different stages of trans-organ migration. The function of these molecules will be validated in physiological environments. This proposal focuses in the role of calcium channels and cytoskeleton rearrangements, two key cellular functions that combined regulate cell contractility, main requirement for cell motility in complex environments. The success of this project might open new possibilities in the treatment of pathologies in which cell motility is altered such as autoimmune diseases or cancer metastasis.