Fig. 1
Lymphatic valves direct migration of filaria larvae toward the lymph node. a Model of primary lymphedema. Success rate for L. sigmodontis filariae migration to the pleural cavity (as % inoculated 10 days earlier) after inoculation in lymphedematous hind paw of Chy3 mice. Totally, 40 filariae were injected in each of 9 control and Chy3 mice (p = 0.0003, one-tailed Mann–Whitney U test). b Model of secondary lymphedema. Success rate for L. sigmodontis filariae migration to the pleural cavity after inoculation into lymphedematous tails. Totally, 40 filariae were injected in 6 (control), 8 (sham), and 4 (lymphedema; p = 0.00021, two-tailed Fisher exact test (3 × 2 table). For a, b, individual results (with means and standard deviations) of two pooled experiments are shown. Source data are provided as a Source Data file. c–h Maximum intensity projections (MIP) of immunostained whole-mounted dorsal ear dermis with migrating filariae. c Left, TRITC-labeled filariae (fila) outside the Lyve1 (Lve1)-stained lymphatics capillaries (Lcap) and collagen IV (Coll IV)-stained collectors (Lcoltr). Mφ-macrophages. Inset. One micrometre optical section shows basement membrane of capillary lymphatic. Right, fluorescent labeling of a larva revealed the presence of anatomical organs and allowed identification of its head-to-tail orientation (Supplementary Note 3). d–h Intravascular larvae were found only in lymphatic precollectors. d Left, In contrast to blood vessels, lymphatic precollectors are weakly stained with VE-cadherin (VE-cad). d Right, Strong signal from collagen IV revealed the characteristic morphology of lymphatic collectors. The larva that is crossing the valve is located at the trunk-side of the lymphatic valve. e–h Valves of lymphatic collectors prevent afferent filariae migration. e, f Insets. Directionality of lymphatic valves on 1.8 µm optical cross-sections. g Three larvae coiled at the post-valve sinus. h The structure of the valve. Surface masks created from the MIP image shown in (g). Migrating larvae have a higher probability of localizing the inlet of the lymphatic trunk than the outlet of the lymphatic sinus because the valve opening occupies a proportionally larger area of the smaller prevalve lymphatic trunk. Blue arrows in (d–g) indicate the original directionality of lymphatic drainage. Blue arrowheads in (h, right) point to the edges of the valve in the trunk (top) and the sinus (middle). Bars = 50 µm
