Figure 3.

L-selectin mediates lymphocyte migration into PLN. Splenocytes isolated from wild type or L-selectin^−/− mice were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE; 0.5 μM, CFSE^high or 0.05 μM, CFSE^low) and injected (40 × 10⁶ cells total) intravenously into recipient mice. Thirty minutes after transfer, the spleen and PLNs from recipient animals were harvested, cryosectioned, and immunostained for fluorescence light microscopy. In the left column, all the injected cells were wild type. Both CFSE^high (bright green, arrowheads) and CFSE^low (dull green, arrows) cells were observed in equivalent numbers in the spleen and PLN of the recipient mice. In the right column, L-selectin^−/− cells were labeled CFSE^high and wild type cells were labeled CFSE^low. While both CFSE^high and CFSE^low cells were observed in the spleen, only CFSE^low cells (wild type) were found within the PLN. Red staining indicates PNAd expression on the HEV.