Age dependent effect of toxic and detoxified endotoxins on the natural anti-DNA antibody level in rats.

: Toxic endotoxin (LPS) and its irradiated detoxified form (RD-LPS) induced only small changes in the DNA level in the sera of 4, 12 and 18 months old rats. Changes in the anti-DNA titres were age-dependent. In 4 months old rats one or two injections of the LPS preparations failed to increase the circulating anti-DNA level. In 12 and 18 months old rats both toxic and detoxified LPS preparations raised the anti-DNA titres. The second LPS injection evoked a smaller response in 18 months old rats than the first one.