Resistance to tuberculosis decreases with age and older animals are relatively susceptible to this infection is the surprising conclusion of Smithburn1 of the Rockefeller Institute, from his study of experimental tuberculosis in guinea pigs.
Statistical and experimental evidence led earlier immunologists to the generalization that resistance to all infectious diseases increases with age, reaching its maximum in early adult life. After the thirty-fifth year a gradual decrease in antimicrobic defense was postulated.
Some doubt as to the universality of this law may arise from study of the relative susceptibilities of young and adult rabbits to streptococcus and staphylococcus filtrates. Up to the age of 4 months newborn rabbits can be injected intravenously with presumably multilethal doses of staphylococcus toxin without appreciable toxic symptoms.2 Adult rabbits are killed within twenty-four hours by a fraction of the same dose per unit of body weight. This youthful tolerance to staphylotoxin is
RESISTANCE TO TUBERCULOSIS. JAMA. 1938;111(7):621. doi:10.1001/jama.1938.02790330041010