Lymph- and blood-borne soluble IgM does not access the conduit system. (A) Unimmunized JHT mice or animals that received an intradermal injection of CFA 10 d before in one ear were injected s.c. with fluorescent WGA (∼38 kD) with or without purified mouse IgM (∼1,000 kD) and their auricular dLNs were harvested at the indicated time points. LN sections were stained for collagen IV (Col.IV) and IgM. Arrowheads indicate SCS. Insets show high-magnification views of the SCS and the underlying cortex. Bars, 100 µm (left panels); 20 µm (right panels). Data are representative of three experiments (two mice per condition and experiment). (B) JHT and WT mice were injected intradermally with CFA in one ear. 10 d later, JHT mice were supplemented with the serum of the immunized WT mice over a 24-h period and injected i.v. with fluorescent WGA 5 min before the harvest of reactive and contralateral auricular LNs. Data show confocal images from LN sections stained for collagen IV, PNAd, and IgM. Insets display high-magnification views of PNAd+ HEVs (yellow dashed line) and surrounding conduits. Bars, 200 µm (left panels); 50 µm (right panels). Data are representative of two experiments (three mice per experiment).
