Figure 2.

C1q interacts with ecto-calreticulin very rapidly after UVB irradiation. JurkaT cells incubated with C1q or its globular region were immunolabeled for Calreticulin (CRT) (A488) and C1q or C1qGR (Cy3) as described in Section “Material and Methods.” (A) Labeling on cells fixed 30 min after UVB irradiation. (B,C) Fluorescence resonance energy transfer (FRET) efficiency was estimated for UVB-irradiated cell and untreated cell by photobleaching of the acceptor dye (Cy3) on non-permeabilized cells. Regions used for the acceptor photobleaching and FRET analysis are shown. Curves correspond to the normalized fluorescence intensities of both dyes (Cy3 in red and A488 in green) expressed as a percent of the signal measured before the gradual photobleaching started (black arrow). (B) FRET efficiency (percent of acceptor fluorescence intensity increase) is expressed as a function of the percent of the normalized acceptor fluorescence intensity. Bars: 11 µm.