*Purpose: Severe primary graft dysfunction (PGD) affects 30% of lung transplant patients. Pulmonary alveolar macrophages play a significant role in lung PGD, but systemic immunotherapy is inadequate in suppressing them. We explored using nanoparticles (NP) as a means of direct allograft immunosuppression delivery.

*Methods: We encapsulated Alexa 594 dye and anti-IL6 receptor monoclonal antibody in poly (lactic-co-glycolic acid) NPs via double emulsion (anti-IL6R-Alexa 594 NP). The lung from one cynomolgus macaque was procured then underwent infusion of lung preservation solution mixed with nanoparticles via direct pulmonary artery cannulation. Samples pre- and post-NP infusion were taken and stained using immunofluorescence techniques. Tissues were stained with antibodies against CD163, vWF, CD11b, CDC11c, HLADR⁺, CD3, and CD20.

*Results: Hydrodynamic size of anti-IL6R-Alexa594 NP was 107 ± 14 nm (polydispersity index: 0.25), transmission electron microscopy size was 98 ± 8.1 nm, and zeta-potential was -3.1 ± 1.2 mV. We confirmed loading efficiency of anti-IL6R-mAb in NP as 23.1 ± 3.8% using bicinchoninic assay. Anti-IL6R-Alexa594 NP showed 50% of drug elution by 4.6 days and 75% of drug elution by 13 days . Anti-IL6R-Alexa594 NP were found in the lung parenchyma and in the hilar lymph nodes. Immunofluorescence staining assay demonstrated that CD163⁺, CD11b⁺, HLADR⁺, and CD11c⁺ cells from hilar lymph node internalized NPs. The same held true for the lung parenchyma tissue with the addition of CD3⁺ cells also having nanoparticle uptake. Approximately 10% of the lymph node macrophages (HLADR⁺, CD11b⁺, CD163⁺) and 50% of the pulmonary macrophages had NP uptake. Figure 1: Immunofluorescence imaging of lung parenchyma. Blue = DAPI, Green = HLADR⁺, Red = NP.

*Conclusions: In this study, we synthesized bright nanovesicles to track the fate of NPs in the lung. These biocompatible NP produced sustained release of their loaded anti-IL6R over the span of two weeks in physiological condition, offering a way to control immune reactions locally. Despite the short perfusion time, a significant number of lung alveolar macrophages were able to phagocytose NPs. This is a promising new avenue for drug delivery in hopes of reducing incidence and severity of lung PGD.

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