the top kidney lymphatic - enriched genes included dnase1l3 ( log 2 fc = 3. 77, p = 3. 24 × 10 ), the chemok ine ccl14 ( log 2 fc = 3. 03, p = 7. 00 × 10 ), the netrin receptor unc5b ( log 2 fc = 2. 26, p = 9. 65 × 10 ), the growth factor midkine ( mdk, log 2 fc = 1. 98, p = 5. 56 × 10 ), and the anti - protease α2 macroglobulin ( a2m, log 2 fc = 1. 80, p = 4. 00 × 10 ). most of these genes were also expressed by blood endothelia in the kidney, whereas a2m was also expressed by stromal cells ( supplemental figure 3d ). among the 251 degs with lower expression in kidney lecs compared with those from other organs ( figure 3d ) were lyve1 and the major neutrophil chemoat tractant cxcl8 ( 65 ), the latter of which was also absent from heart, lung, and intestinal lecs. conversely, lecs in these visceral organs expressed the alarmin cytokine il33 ( 66 ), which was reduced in lymphatics of the skin and breast ( figure 3d and supplemental figure 3e ). to provide pathological context to the kidney lymphatic degs, we examined their expression in nephroseq, a gene expression database of kidney diseases. dnase1l3 was significantly upregulated in the tubulo interstitium of patients with lupus nephritis ( n = 31 ) compared with controls ( n = 8, mean difference in log 2 expressio n = 1. 1 ± 0. 34 – 1. 9, p = 0. 0013 ) ( figure 3e ). conversely, mdk was significantly upregulated in several inflammatory and metabolic kidney diseases, except for minimal change disease ( figure 3f ). collectively, our analyses demonstrated that kidney lecs have an organ - specific molecular profile, enriched for dnase1l3, mdk, and ccl14, with reduced expression of canonical immune trafficking markers such as lyve1 and cxcl8. lymphangiogenesis has been observed during transplant rejection in both rodent models ( 23, 25, 31, 67 ) and humans ( 24, 26 – 28 ), but whether this is protective or promotes alloimmunity remains unclear. to investigate this in the human context, we profiled kidney transplants with chronic mixed rejection, a setting in which both donor - specific antibod ies and t cells target hla molecular expressed on tubular epithelial and blood endothelial cells. we analyzed 3 allografts with histological features consistent with chronic mixed rejection, including t cell – and antibod y - mediated injury ( supplemental table 2 ), and compared them with control kidneys obtained from nontransplanted donor organs. in rejecting allografts, the lymphatic vascular network exhibited marked disor ganization, with loss of the hierarchical structure observed in controls ( figure 4a ). quantitative analysis revealed a 7 - fold increase in mean lymphatic vessel density ( 95. 12 ± 49. 21 vs. 690. 3 ± 121. 6 vessels / mm, p = 0. 0014 ), accompanied by reductions in the distribution of vessel lengths ( median difference = 132 vs. 68. 4 μm, p = 0. 0001 ), vessel radius ( 9. 05 vs. 4. 9 μm, p < 0. 0001 ), and branching angle ( 112 versus 103, p < 0. 0001 ) ( figure 4b and supplemental videos 5 and 6 ). notably, lymphatic vessels also infiltrated the allograft medulla, a region devoid of lymphatics in healthy kidneys ( figure 4, c and d ). lec - cell junctions are key regulators of immune cell trafficking. in homeostasis, these junctions form discontinuous “ button - like ” structures that facilitate leukocyte entry into lymphatics, whereas during chronic inflammation, they transition into continuous “ zipper - like ” formations that impair lymphatic drainage ( 68 – 70 ). given the accumulation of infiltrating lymphocytes in chronically rejecting grafts ( 71 – 73 ), we hypothesized that altered lymphatic junctional architecture might be a feature of rejection. to assess this, we immunostained for vascular endothelial cadherin ( cdh5 ), a key component of endothelial junctions ( supplemental video 7 ), and used pdpn to disting uish lymphatics from blood vessels ( supplemental figure 4 ). discontinuous cdh5 lec junctions were quantified in both control ( figure 4e ) and chronic rejection ( figure 4f ) samples, and values were normalized to total lymphatic network volume ( figure 4g ). we observed a reduction in disconnected ( button - like ) junctions in rejecting allografts compared with controls ( figure 4h, mean difference = 2. 7 × 10 ± 7. 3 × 10 cdh5 junctions per mm lymphatic vessel ), consistent with a shift toward a zipper - like configuration. given the structural perturbation of kidney lymphatics in rejecting allografts, we next examined their spatial relationship to organized immune responses within chronic rejection. a hallmark of alloimmunity is the formation of tertiary lymphoid structures ( tlss ), ectopic lymph node – like aggregations of t cells and b cells, where follicular dcs and high endothelial venules ( hevs ) also develop. tlss facilitate local antigen presentation and lymphocyte activation, and they have been associated with progressive graft injury and dysfunction ( 74 – 79 ). using tripl e immunolabeling, we found pdpn lymphatics were observed close to cd4 t cell – and cd20 b cell – rich aggregates ( figure 5a ) in 3 rejecting allografts, consistent with previous reports ( 26 – 28 ). to assess the relationship between lymphatics and tls maturation, we examined pdpn lymphatics relative to cd21 follicular dcs and peripheral lymph node addressin ( pnad ) hevs, the latter serving as a marker of mature tls ( 67, 80, 81 ). the lymphatic network in rejecting allografts interconnected multiple mature tlss containing hevs ( figure 5b and supplemental video 8 ). such connections were not detected between cd31 vessels ( supplemental figure 5a ). spatiotemporal analysis revealed that all identified tlss were near lymphatic vessels ( figure 5c ) ( n = 9 / 9, 100 % ), whereas only half contained hevs ( n = 5 / 9, 55. 6 %, p = 0. 023 ). in mature tlss with hevs, pdpn lecs were significantly closer to the tls core than hevs ( figure 5d, mean distance = 49. 53 ± 23. 83 μm vs. 109. 6 ± 25. 13 μm, 95 % ci = 24. 33 – 95. 76, p = 0. 0047 ), suggesting that lymphatics are an early feature of tls organization. to explore lymphatic - lymphocyte relationships beyond defined tls regions, we performed 3d imaging and spatial quantification of pdpn lymphatics relative to cd20 b cells and cd4 t cells ( figure 6, a and b, and supplemental video 9 ). intraluminal cd20 b cell density was reduced by half in rejecting allografts compared with controls ( figure 6c ), although total b cell numbers were equivocal, suggesting that this reflects increased lymphatic volume rather than changes in b cell abundance. in contrast, total intraluminal cd4 t cells increased in rejecting kidneys, with a 3 - fold increase in cd4 t cell density ( figure 6d ) relative to controls, a markedly higher density than was detected in the surrounding allograft parenchyma. to further assess how lymphocyte position relative to lymphatics is altered in rejection, we performed spatial statistical analysis, by computing a normalized distance metric for each b cell ( figure 6e ) and t cell ( figure 6f ) to its nearest lymphatic vessel, and comparing this to a null model of random spatial distribution ( 82 ). cd20 b cells showed no significant spatial association with lymphatics in either control kidneys ( n = 703 cells; p = 0. 631 ) or rejecting allografts ( n = 2, 963 cells; p = 0. 326 ) ( figure 6g ). however, cd4 t cells ( n = 2, 149 cells across 2 controls ) had a peak distribution within 0 – 100 μm from the nearest lymphatic vessel and were significantly enriched near lymphatic vessels compared with a random distribution ( p = 0. 029 ). this association was lost in rejecting allografts ( n = 4, 382 cells, p = 0. 699 ) ( figure 6h ), indicating disrup ted t cell – lymphatic proximity in the context of chronic rejection.