Fig. 5.

FHR1 binds to necrotic cells and triggers IL-1β release by monocytes. a, FHR1, but not FH binds necrotic HUVECs, as shown by flow cytometry. b FHRB binds to necrotic but not healthy mouse alveolar macrophages, FHRB antiserum was used for flow cytometry. c FHR1 (green) binds to necrotic cells. DNA (blue) is stained with DAPI and membrane (red) with WGA. Scale = 10 µm. d FHR1 and FH from NHS bind to necrotic, but not to healthy cells. One representative western blot of three is shown. e FHR1 bound to C3b does not induce IL-1β release by monocytes. f FHR1 SCR1–2 binds to necrotic HUVECs. g FHR1 bound to necrotic HUVECs triggers IL 1β in monocytes. h IL-1β release in response to necrotic HUVECs is reduced in ΔFHR1/3 NHS compared to NHS. i Reconstitution of FHR1 in ΔFHR1/3 NHS increased IL-1β release by monocytes. FH has no effect. j Complexes (red) of FHR1 (on necrotic cells) with EMR2 receptor (on monocytes) in whole blood. Total picture fluorescence intensity of single cells (n = 14 for FHR1/3, n = 10 for ΔFHR1/3) were analyzed using unpaired two-tailed t-test. Data in a–i represent the mean ± SEM of three to four independent experiments with different cell donors. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 (unpaired two-tailed t-test)