Figure 2.

Dual-color fluorescence intensity histogram. mAbs 3F4-Alexa488 and 12F10-Cy5 were added to pooled CSF of control patients that was spiked with prion rods derived from scrapie-infected hamster brain at various dilutions (A, 1:1,000; B, 1:100,000; C, no rods) or aggregates of Aβ (1–42) peptide at a concentration of 1 μM (D). (E) Unspecific antibody probes mAb(Aβ)-Alexa488 and mAb(IL-8)-Cy5 were added to prion rods diluted 1:1,000 in CSF. Samples were measured for 600 s with a channel time of 500 μs in an open volume element moving at 1 mm/s. Each dot represents a pair of fluorescent intensities. The number of channels is color-coded on a logarithmic scale. (F) Schematic representation of an intensity histogram. Low-intensity fluorescent signal of probe molecules (gray) is separated from unspecific aggregates incorporating only one type of label (red). Channels with a high-intensity signal in both colors above a linear cutoff (yellow) are summed for quantitative analysis (see Fig. 3). F_red, red fluorescence; F_green, green fluorescence.