IN VITRO STUDIES ON INTERACTIONS BETWEEN MACROPHAGES OF RABBITS AND TUBERCLE BACILLI .2. CELLULAR AND HUMORAL ASPECTS OF ACQUIRED RESISTANCE

Abstract

In vitro studies demonstrated that BCG vaccination confers on the macrophages of both market rabbits and inbred, susceptible rabbits an ability to retard the intracellular multiplication of tubercle bacilli H37Rv. The macrophages of vaccinated, natively susceptible rabbits showed no sign of cytotoxic injury due to ingested bacilli when cultured in the absence of immune serum. Serum from natively susceptible rabbits 2 weeks after BCG vaccination could, at least to some extent, protect the normal unvaccinated, susceptible host cells from degenerative effect due to intracellular infection. Serum from BCG-vaccinated market rabbits also protected against cytotoxic injury in the macrophages of normal market rabbits which behaved like natively susceptible hosts. Whether the resistance to cytotoxic damage exhibited in immune host cells was an inherent change in the cells as such, or was merely due to an adherence of an immune humoral factor, is not known. Nevertheless, the presence of immune serum did not alter the rate of intracellular multiplication of the parasite. It is believed that the failure to observe cytotoxic damage in vivo is due to the masking effect of immune humoral protection.