Employing a model cell system that demonstrated T-cell-receptor-mediated apoptosis, the authors studied the genes that code for proteins involved in apoptosis. Based on a series of measurements in which various proteins were added to or removed from the model cell system and the consequences on apoptosis noted, it was concluded that the products of two particular genes, ALG-2 and ALG-3, were involved in apoptosis. Further measurements established that one of the proteins was a Ca2+-binding protein, and that ALG-3 was the mouse homologue of a human gene linked to Alzheimer's disease. Since the evidence linked the gene to apoptosis, it was concluded that cell death might play a role in Alzheimer's disease.