Retention of bacterial lipopolysaccharide at the site of subcutaneous injection

The tissue distribution of Klebsiella pneumoniae O3 lipopolysaccharide (KO3 LPS) was studied in mice injected subcutaneously (s.c.) or intraperitoneally (i.p.) with 125I-labeled KO3 LPS. Marked retention of KO3 LPS radioactivity could be found at the site of s.c. injection for several weeks. On the other hand, about 85% of the radioactivity rapidly disappeared from the peritoneal cavity within 6 h after i.p. injection. The long-term presence of KO3 LPS at the injection site was also supported by experiments with 51Cr-labeled KO3 LPS and immunoblotting and immunofluorescence staining methods. The R-form LPS lacking the O-specific polysaccharide chain of KO3 LPS and the lipid A fraction of KO3 LPS seemed to remain at the site in larger amounts and for longer times than KO3 LPS. There were no marked differences in the retention pattern at the injection site among KO3 LPS, Escherichia coli LPS, Salmonella typhosa LPS, and Salmonella enteritidis LPS. However, much less radioactivity accumulated in the livers and spleens of mice injected with either KO3 LPS or S. typhosa LPS compared with the other LPS preparations. It was suggested that retention of LPS at the site of s.c. injection may play an important role in the development of various biological actions of s.c. injected LPS.