Immunofluorescence of prolactin and the prolactin receptor in breast cancer cell lines. Dual-fluorescence immunocytochemistry for the prolactin receptor (PRLR) and prolactin in breast cancer cell lines. Cells were plated onto eight-well chamber slides at identical cell densities and were allowed to adhere for 48 hours prior to fixation and staining (see Materials and methods). Top row, 4',6-diamidino-2-phenylindole; second row, PRLR–Texas red; third row, prolactin–Fluorescein isothiocyanate (FITC) (green); fourth row, merged images. (a) Negative controls photographed with identical exposure and processed with identical software settings, compared with antibody-positive samples shown in subsequent columns: (b) T47D cells, (c) MCF-7 cells, (d) MDA-MB-468 cells, (e) MDA-MB-453 cells, and (f) SKBR3 cells.