Figure 1

Expression of PD-L1 in colon sections is higher in septic compared with nonseptic ICU patients. Colon histological sections were stained for PD-L1. Four to six grayscale images were acquired per specimen with a Nikon E800 microscope using a 20 × PlanApo objective and a Spot RT3 camera. Positive staining was defined through intensity thresholding, and mean intensity measurements were recorded. Data were expressed as the total area stained on a pixel-by-pixel basis. (A) There was no difference between the septic and nonseptic groups related to age (55.9 years versus 53.7 years; p = 0.8) or gender (female, 60% versus male, 67%; p = 1). (B) Significantly higher PD-L1 staining was shown in the area of abnormality compared with the normal margin of septic patients (n = 5), while no change in PD-L1 intensity in nonseptic patients was evident (n = 6) (C). The calculated extent of change in pixel intensity (Δ pixel) between the two areas in the same patient were significantly higher in septic versus nonseptic patients (D), * P < 0.05, nonpaired t test. (E) Representative images of PD-L1 staining from the patients. Panels E1 and E3 show normal margins from septic and nonseptic patients, respectively. Panel E2 shows the area of abnormality from a septic patient, and panel E4 is the area of abnormality from a nonseptic patient. Original magnifications × 200.