Immunohistochemical Localization of GM-CSF in the Bovine Uterus
Immunostaining for GM-CSF was observed in the con-ceptus at the surface of the trophectoderm at d18P (Fig. 4F) and sometimes in d21P-d24P in regions where the attachment process was not advanced (Fig. 6F). In maternal tissues, GM-CSF staining was concentrated in the apical portions of the LE and glandular epithelium, as well as in the basement membrane (Fig. 4). The staining grades were similar to those observed with COX-2: LE > SG > DG > S.
However, expression levels were similar among these tissue types at d16P (Fig. 4E and 6C) and darker in SG compared with LE at d30P (not shown). On the other hand, the myometrium was positive only at d30P (Fig. 6D). GM-CSF expression in the stroma could mainly be credited to capillaries, leukocyte-like cells, and fibroblasts in the stratum compactum. In all cell types, GM-CSF was clearly confined to the cytoplasm. No difference was observed between ca-runcular and intercaruncular regions (not shown). The strong signal typical of the LE also decreased at attachment sites in syncytial regions (Fig. 4, H and I). An example of ‘‘advanced’’ fusion at d21P between trophoblast and LE is illustrated in Figure 6E (vs. Fig. 4G), along with an unfused region that probably comes from the extremities of the con-ceptus at d24P (Fig. 6F vs. Fig. 4H). Control IgG1, targeting a nonmammalian protein, was negative (Fig. 6H).