| Abstract: | The phenomenon of lipopolysaccharide (LPS)-induced hyporesponsiveness has been reported to occur in macrophage cell lines and primary cells. Hyporesponsiveness was evidenced by a diminution or lack of production of tumour necrosis factor-alpha (TNF-alpha) after sequential doses of LPS. In order to characterize the hyporesponsive state in Kupffer cells, the production of TNF-alpha was quantified after varying the concentration of a primary low dose of LPS prior to a challenge with a high, normally stimulatory dose of LPS. The kinetics of establishment of the hyporesponsive state and the effect of varying the bacterial serotype and genus of the challenge dose were determined. The specificity of the hyporesponsive state for LPS was examined. Our results demonstrate that complete hyporesponsiveness with no detectable production of TNF-alpha (< 30 pg/ml) was achieved after a primary dose > or = 10 ng/ml. Establishment of the hyporesponsive state took place within 6 hr. Induction of hyporesponsiveness was not dependent upon the serotype or genus of the challenge dose of LPS and was not specific for LPS. Complete hyporesponsiveness was induced after a primary dose (10 micrograms/ml) of the Gram-positive bacterium Corynebacterium parvum (Cp) and was evident upon challenge with 100 micrograms/ml Cp. The data indicate that the mechanisms by which LPS and Cp induce hyporesponsiveness are not identical in that a primary dose of LPS (10 ng/ml) induced only partial hyporesponsiveness upon challenge with Cp (100 micrograms/ml). These studies improve our understanding of Kupffer cell function. |
