Interferon and cytotoxic factor (cytotoxin) released in the blood of mice infected with Mycobacterium bovis BCG. I. Enhanced production of interferon and appearance of cytotoxin stimulated by capsular polysaccharide of Klebsiella pneumoniae or bacterial lipopolysaccharide.

Interferon production stimulated by the active substance (neutral fraction) of the capsular polysaccharide of Klebsiella pneumoniae (neutral CPS-K) in BCG-infected mice was compared with that by bacterial lipopolysaccharide (LPS). Prior infection with BCG increased the responsiveness of mice to the lethal effect of neutral CPS-K as well as to that of LPS. Associated with this, BCG-infected mice showed a markedly enhanced ability to produce interferon after stimulation not only by LPS but also by neutral CPS-K. In addition, a cytotoxic factor (cytotoxin) was found to be released in the serum of BCG-infected mice after injection of these inducers. The kinetics of production of interferon and cytotoxin stimulated by neutral CPS-K were very similar to those stimulated by LPS. The time pattern of cytotoxin production was not in parallel with that of interferon production. Interferon reached a peak 2 hr and cytotoxin 3 hr after injection with these inducers. Interferon and cytotoxin produced by neutral CPS-K showed essentially the same stabilities to heating at 56 C and to treatment at pH 2 respectively as those produced by LPS. Interferon was inactivated by heating at 56 C more rapidly than cytotoxin. Cytotoxin was inactivated by treatment at pH 2 for 24 hr, whereas interferon activity was well preserved after this treatment. These results suggest that both activities are the result of different substances.