Fig. 5. Transcytosis and recycling of IgG by FcRn and FcRn–GFP in MDCK monolayers. FcRn- and FcRn–GFP-expressing cells were grown on filters. The pH of the loading side was adjusted to pH 6.0 or pH 7.3 as indicated, and the pH of the non-loading side was maintained at pH 7.3. Rat [¹²⁵I]IgG (100 nM) was added to the loading side and the media at the loading side (for recycling) and the non-loading side (for transcytosis) was removed and counted at 2 min intervals. The mean of triplicate measurements is plotted along with the standard deviation for each time point. Some measurements were conducted using cells treated with 150 nM wortmannin. The effects of wortmannin were maximal at 150 nM, but inhibition of apical to basolateral transcytosis was also observed in cells treated with 50 or 100 nM wortmannin (data not shown).