Abstract: The ability to determine the stage or pathway of cysteine proteases in a single cell assay has long been desired as a material event in apoptosis. The present invention relates to a method and assay reagents for determining enzyme activity and relating said activity to the apoptotic pathway. In addition, the method find utility in distinguishing apoptotic activity from necrotic activity.

Abstract: The invention provides a cell control product for use with a cytoenzymology assay to confirm enzymatic activity in devices employing electronic and/or optical means. The cell control product comprises a lyophilized mammalian cell which is capable of being rehydrated in water to exhibit cellular structure and cellular enzymatic activity so that said lyophilized cells can function effectively as a cytoenzymology cell control in an enzymatic analysis. The cellular structure of the cell control is capable of being authenticated by light scatter or microscopy analysis and the cellular enzymatic activity is capable of being authenticated by fluorescence analysis. The cell control exhibits a real time stability when stored at between 2 and 8.degree. C. for at least a two month period of time. Preferably the mammalian cell is an abnormal cell selected from Molt 4, CCRF-CEM and HL-60 cell lines.