Impaired survival of growth factor–deficient mouse strains. Mixed-gender cohorts of wild-type (n = 60), GM−/− (n = 44), G−/− (n = 62), and G−/−GM−/− (n = 53) mice were set aside after successful weaning and studied until death or distress necessitating killing. Survival is plotted according to the method of Kaplan and Meier, and P values are based on comparisons using the log-rank test. Survival of G−/−, GM−/−, and G−/−GM−/− strains was impaired relative to wild-type mice (P < .0001). Survival of G−/−GM−/− mice was inferior to both G−/− and GM−/− animals (each P ≤ .022).