Immunological nature of antimycobacterial phenomenon in macrophages.

Heptane-extractable fractions (HEF) prepared from immune-activated macrophages (IA-M) of tubercle bacilli or bovine gamma globulin-sensitized and -challenged guinea pigs inhibited the growth of tubercle bacilli whereas HEF of normal macrophages exerted no antibacterial activity. In distinction to the strong antibacterial activity of HEF of IA-M, HEF of immune macrophages exerted weak or no antimycobacterial activity. HEF of alveolar macrophages exerted stronger antibacterial activity than HEF of peritoneal macrophages. The degree of the antibacterial activity of HEF was determined primarily by the time of macrophage collection from antigenically stimulated animals. The antibacterial activity gradually increased and peaked at 2 weeks after the antigenic stimulation of sensitized animals; subsequently, the activity declined and disappeared in about 5 weeks. Similar to other immunological reactions, the stimulation of sensitive animals with specific antigen induced an anamnestic reaction which was characterized by a rapid recall of the macrophage antimycobacterial phenomenon (MAP). The antibacterial strength of the recalled phenomenon in sensitized animals was dependent upon the intensity of the sensitizing regimen; the phenomenon was much stronger in three times-sensitized animals than in once- and twice-sensitized animals. The time of appearance and the specificity of induction and of recall of the MAP indicate that the phenomenon is associated with the activated state in macrophages and, as a consequence of this association, it has a well-defined immunological nature.