Figure 1.

Podocytes ingest both labeled latex beads and soluble ovalbumin. Antigen uptake by conditionally immortalized murine PCLs was analyzed by FACS and is shown by a clear shift in the respective histograms. (A and B) The uptake of particles or soluble protein by different primary cells was visualized by microscopy. (C and E) Uptake rates of isolated primary podocytes, (D) isolated primary podocytes together with mesangium cells, and (F) BMMs were compared. The cells were incubated with (A and C) Alexa647, (D) Texas red-labeled ovalbumin, or (B, E, and F) yellow-green–labeled latex beads. We found that podocytes could ingest both labeled latex beads and soluble fluorescence-labeled ovalbumin. Labeled ovalbumin was incorporated by podocytes (white arrows in D). In contrast, mesangial cells, marked by asterisks and distinguished by the bigger nucleus in D, did not. Furthermore, (E) primary podocytes phagocytosed 1.0-µm beads to the same extent as (F) BMMs. Control staining was performed as shown in Supplemental Figure 5. The phagocytosis in vivo was shown by injecting 1.0-µm latex beads intravenously. After 24 hours, the mice were euthanized and analyzed histologically. The uptake of fluorescent particles into podocin- or podocalyxin-positive cells is shown in G and H.