I am performing a transient transfection of my protein of interest tagged with GFP in HeLa cell line to determine whether overexpression of my protein of interest is leading to induction of apoptosis. 48 hours post transfection, i am fixing the cells and staining with anti cleaved caspase 3 antibody. but when visualizing under microscope i am seeing all the cells be it transfected or untransfected are showing a staining of caspase 3, which is a grainy staining in the cytoplasm. Can anyone please help me to understand where i am going wrong with my experiment so as to get such staining of cleaved caspase 3 in all the cells?