Glucocorticoid receptor expression in 13-day old rat fetal liver cell progenitors (CD45⁺) (b) and 15-day old rat fetal thymocytes (d). Both sorted 13-day old fetal liver CD45⁺ cells and 15-day old fetal total thymic cells were cytospun, fixed, and incubated with a biotin-conjugated MoAb specific for rat GR (BuGR2) followed by avidin-Texas red staining. An isotype-matched irrelevant antibody was used as negative control to define background fluorescence (a and c). The cells were observed and photographed under a fluorescence Labophot-2 microscope. Original magnification × 300.