Species and strain differences in the lethal factor of the mouse submandibular gland

The differences in susceptibility of animals to the lethal factor extracted from the mouse submandibular gland and magnitude of its lethality were compared among various species, strains, ages, and sex of mice. Comparisons of LD50 values computed by an IBM 360/System computer using a programmed probit analysis yielded the following significant results. The lethal factor of adult male mice was lethal to all species and strains of animals tested. Strain differences were observed in five inbred strains of mice, and varying degrees of resistance against the lethal factor were demonstrated. The lethality was strongest in the submandibular gland of our subline BALB/c mice, and the highest susceptibility to the lethal factor was demonstrated by female C57BL mice. This factor was found to be lethal not only to mice but also to other species of animals, Mongolian gerbils being most susceptible and New Zealand rabbits next.