Exogenous reinfection in experimental airborne tuberculosis.

This study of experimental airborne tuberculosis in which guinea pigs were infected with tubercle bacilli of low and high virulence, provides no support for hypotheses suggesting that a second or third exposure to tubercle bacilli leads to an adverse effect on host response to the first infecting strain or to the reinfecting strain. The principal influence of the first infection was to protect against a subsequent infection. This protection was most evident as inhibition of the spread of bacilli from the lungs to the spleen. The first infection appeared to exert less influence on events at the site of reimplantation of organisms in the lungs.