Dab2 immunoreactivity in mononuclear phagocytes. A-A": Double labeling (immunofluorescence staining) on a sagittal section through an E10.5 embryos shows co-localization of Dab2 (green, arrows in A) and Iba1 (red, arrows in A') in mononuclear phagocytes (yellow, arrows in A") within the neural tube (Ne, white outline), and in fetal macrophages outside the neural tube. B: Double labeling shows that Dab2 immunoreactivity (green, indicated by arrows) does not overlap with PGP9.5 immunoreactivity (red) within the neural tube (white outline) in a sagittal section through an E11.5 embryo. C: Double labeling at E12.5 shows Iba1+/Dab2- microglial progenitors (arrows, red) within the neural tube (Ne) and Iba1+/Dab2+ fetal macrophages (arrowhead) in the adjacent mesenchyme (mes).D-F: Sagittal sections show that Dab2+ cells (arrows) are often closely apposed to blood vessels (arrowheads) within the neural tube at E10.5 (D) and E11.5 (E), but more scattered by E12.5 (F). G: Some Dab2+ cells (arrowheads) are also observed closely associated with the roof of the fourth ventricle (4V). H-H": Double labeling for Dab2 (green, H) and Iba1 (red, H') at E14.5 shows that Dab2 is only expressed in Iba1+ fetal macrophages (arrows) in the mesenchyme (mf: mesencephalic flexure, white outline) outside the neural tube (Ne) but absent in Iba1+ microglial progenitors within the neural tube. I: At E16.5, Dab2 expression is detected in the wall of blood microvessels (arrowheads), but Dab2+ microglial progenitors are no longer detectable at this stage of development. J, K: Sections of an adult brain show Dab2+ perivascular cells (arrowheads in J) and Iba1+ microglia (arrows in K). L-L": A merged image (L") shows co-localization of F4/80 protein (red, L') in some (arrows in L") but not all of the Dab2+ (green, L) cells lying on the wall of cerebral microvessels (mv, white outline). M: A sagittal section of an E9.5 embryo shows Dab2+ cells in the cranial mensenchyme (mes) outside the neural tube (Ne). N-N": A merged image at E9.5 shows complete co-localization (yellow, brightfield, arrows in N") of Dab2 (green, arrows in N) and Iba1 (red, arrows in N') immunoreactivities in fetal macrophages outside the neural tube (Ne, white outline). O-O": A section through an E14.5 choroid plexus shows complete co-localization (yellow, O") of Dab2 (green, O) and F4/80 (red, O') immunoreactivities. Arrowheads in O' and O" indicate autofluorescence from red blood cells. DAPI counterstained in B, C, H", L". Scale bar: 50 μm.