(A) Representative immunofluorescence images of C3d deposits on hypothermia-stressed Colec11^–/– RTECs following incubation with 10% fresh mouse serum from normal (NMS), Colec11^–/–, Masp2^–/–, or C4^–/– mice, demonstrating C3d deposition following incubation with NMS and reduced deposition with Colec11^–/– or Masp2^–/– serum; in contrast, C3d deposition was not reduced following incubation with C4^–/– serum. Scale bars: 25 μm. (B) Quantification of C3d deposits on the RTECs shown in A. Data shown are from 10 individual images for each of 4 independent experiments. Percentage of C3d-positive binding to Colec11^–/– RTECs was determined from 5 to 7 individual fields, representative of 4 independent experiments, except for incubation with C4^–/– serum, which was performed in 2 of those experiments. *P < 0.05, by 1-way ANOVA. (C) Representative fluorescence images of CL-11 (red), C3d (green), and a merged image of CL-11 and C3d in Colec11^–/– RTECs that had been hypothermia stressed, pretreated with α-L-fucosidase or β-gal, and then incubated with NMS, demonstrating that CL-11 binding and C3d deposition were reduced by fucosidase treatment. A negative control of α-L-fucosidase–treated Colec11^–/– RTECs, which had been incubated with Colec11^–/– serum, is also shown. Scale bars: 25 μm. (D) Quantification of CL-11 binding and C3d deposition in the RTECs shown in C. Data shown are from 6 to 8 individual images and representative of 3 independent experiments. ****P < 0.001, by 2-way ANOVA. (E) Typical staining pattern for C3d on stressed Colec11^–/– RTECs that had been incubated with medium alone or medium containing rCL-11 and then washed and subsequently incubated with Colec11^–/– serum. (F) Quantification of C3d deposition in the RTECs shown in E. Data are from 6 individual images for each of 2 independent experiments. **P < 0.01, by unpaired, 2-tailed Student’s t test.