Detection of active caspase-3 in CL derived from WT and caspase-3-deficient mice following treatment with IgG, Jo2 or PGF2α. The presence of active caspase-3 was evaluated by immunohistochemistry using CM-1 antibody in sections of CL derived from WT or caspase-3-deficient mice 8 h following injection at 48 h post ovulation with IgG (A and B), Jo2 (C and D) or PGF2α (E and F). Original magnification: × 600. The insets represent a high magnification (original magnification × 1000) demonstrating the presence or absence of CM-1 positive cells (dark brown reaction). Medial sections were obtained from CL from three independent mice for analysis. Photomicrographs shown are representative of identical results in at least three separate experiments.