A form of runt disease has been produced in neonatal CF-1 and ICR mice by the repeated injection of 109 washed, autoclaved, saline-suspended staphylococci or streptococci. The most severely affected animals showed a marked decrease in lymphoid tissues and resembled grossly and microscopically animals suffering from the classical runt or wasting disease described by others. The timing of the initial antigenic stimulation was of importance, and animals started on their course of injections at an age of 48 hours or older showed no effect. There was a considerable variation in the severity of the disease within litters and from one litter to another. This variation could not be ascribed to a difference in susceptibility between sexes, since both male and female mice were observed to runt under appropriate conditions. Germ-free ICR mice were much more resistant to the runting phenomenon than conventional animals of the same strain, but could be induced to runt by injection of the staphylococcal vaccine suspended in homologous antiserum.
The relationship of the runting phenomenon described here and classical runt disease or runting by adrenal hormones is discussed.