CORE B - SUMMARY/ABSTRACT Lymph nodes (LNs) play a pivotal role in regulating alloimmune responses. The overall goals of this core are (i) to develop innovative nanodelivery strategies to reprogram the stroma of aged LNs and (ii) to carry out advanced immune imaging for the homing of aged immune cells to the LNs and their interactions within the LNs. Targeted delivery of therapeutics to the LN and reprogramming of its stroma would not only inhibit the priming of alloreactive T cells, but also antagonize memory T cells. Central memory T cells require less stringent activation stimuli to generate vigorous immune responses. Since memory T cells represent the main barriers to tolerance induction, therapeutic strategies that specifically target memory T cells address a high unmet need in heart transplantation. On the other hand, LNs become the primary sites of Treg formation when tolerogenic therapies are used. The main goal of Core B is to establish a method of targeted delivery of immune therapeutics to the LN to facilitate transplant tolerance by reprogramming the LN stroma. Core B will be responsible for the nanoformulation of immune therapeutics proposed in these projects. Core B will also fully characterize these nanoproducts regarding important parameters such as size, shape, charge, stability and release kinetics. Nanomedicine has great potential for developing site-specific targeted delivery of therapeutics. We are using a well-defined, specific delivery strategy that targets glycoprotein molecules known as peripheral node addressin (PNAd), expressed by very specialized veins present exclusively in the LNs, referred to as high endothelial venules (HEVs). Core B will be generating nanoparticles (NPs) encapsulated with various payloads and coated with MECA-79 mAb, which recognizes PNAd molecules on HEVs. The overall hypothesis of Core B is that targeted delivery of immune therapeutics to LNs via HEVs permits specific deposition of payloads to the LNs, with the ultimate goals of suppressing alloreactive T cells and promoting graft acceptance. On the other hand, advanced immune imaging of LNs can provide unparalleled information on the trafficking properties of aged immune cells across aged HEVs. These studies can also comprehensively assess their live interactions within the aged LNs. In addition, these advanced imaging studies of LNs can provide novel information on the impact of therapeutics used in this project on immune cell homing and their interactions within the LNs. Therefore, Core B will have two aims: (i) targeted nanodelivery of therapeutics to aged LNs and (ii) advanced live immune imaging of LNs for immune cell and NP trafficking.