Figure 1

Macrophage and eosinophil distribution during mammary gland development and differentiation. (a-e) Longitudinal paraffin section of a terminal end bud (TEB) was stained twice, first with hematoxylin/eosin (H/E) (d) and then, after destaining, by immunostaining with anti-F4/80 antibody and counterstaining with hematoxylin (a-c). The F4/80⁺ cells were detected with a peroxidase-coupled detection system (brown coloration). (b,c,d) High-magnification pictures of (a): (b) bottom frame; (c,d) top frame. The pictures of doubly stained cells show the cross-reactivity of anti-F4/80 antibody for macrophages (b, filled arrowheads), mainly seen in the neck of the TEB (bottom frame, a) and for eosinophils (c,d, empty arrowheads), mainly seen around the head of the TEB (top frame, a). F4/80⁺ eosinophils were distinguished from F4/80⁺macrophages by their characteristic eosin-pink cytoplasmic granules (d, empty arrowheads) and their segmented nucleus, sometimes in a ring shape with a round cytoplasmic shape (b,c,d, empty arrowheads). In contrast, F4/80⁺ macrophages have a large, oval nucleus with a spread cytoplasm (b,c, filled arrowheads) containing no eosin-pink cytoplasmic granules. (e) The presence of macrophages inside the TEB, where they engulf apoptotic epithelial cells. (f-h) F4/80 immunostaining of mammary sections at day 16 of pregnancy (f,g) and day 2 postpartum (h). Note the abundance of macrophages tightly associated with the lobulo-alveoli during pregnancy and lactation. Original magnification: a, f, h, 400×; b, c, d, e, g 1000×. Panels a-e modified from [7].