T Cell dependence of macrophage activation and mobilization during infection with Mycobacterium tuberculosis

Abstract

Mice made T cell deficient as adults by thymectomy and lethal irradiation, and infected with Mycobacterium tuberculosis, showed a greatly reduced capacity to develop nonspecific resistance to challenge with a heterologous bacterium. The capacity to develop nonspecific resistance was restored, however, by an infusion of syngeneic thymocytes. Evidence was presented which showed that the capacity of mycobacterial infected mice to resist a lethal challenge with a heterologous organism rested on the capacity of macrophages existing at the time of challenge to reduce the number of challenge organisms to a sublethal level within 8 hr. This antibacterial activity of macrophages was substantially reduced in T cell deficient mice but could be restored by an infusion of syngeneic thymocytes. It was concluded that T cell deficient mice have a reduced capacity to mobilize and activate macrophages because of their reduced capacity to respond immunologically to antigens of Mycobacterium tuberculosis.