Figure 2.

Podocytes activate CD4+ T cells by MHC II presentation. BMMs or PCLs were cultivated for 1 day in the presence or absence of ovalbumin. The cells were intensely washed, and 5×10⁵ OT-II cells, purified by magnetic cell sorting, were added at a ratio of 1:1. (B) Supernatants were collected after 48 hours and analyzed for IL-2 and IFN-γ expression by ELISA. Proliferation was measured by ³H uptake, and the CD25 upregulation was analyzed after 48 hours. (A) PCL cells loaded with ovalbumin induced proliferation of ovalbumin-specific MHC class II-restricted CD4+ T cells from OT-II mice in a dose-dependent manner comparable with C57BL/6 BMMs, whereas BALB/c BMMs did not. *Significant differences to medium alone or podocytes without ovalbumin (P<0.05, t test). C shows a representative FACS staining, and D shows quantification of three experiments determining surface expression of the T cell activation marker CD25.