The interaction between lipopolysaccharides and host leucocytes

• Main Author: Urayet, Abdurrazag
• Published: University of Edinburgh 1996
• Subjects: 616.9
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663151

Gram-negative septic shock is a life threatening disease associated with high mortality, particularly in immunocompromised patients. The aim of this project was to investigate the interaction of various forms of LPS - free, membrane associated and as a component of whole bacteria- with mammalian cells to determine the cell surface molecules involved and to study the spectrum of mediators released. An attempt was made to investigate whether human monocytes/MØs produce NO in response to different forms of LPS. NO production was assayed by measuring nitrate, a stable metabolic product of NO, in macrophage culture supernatants. Preliminary work was performed using MØs from several mice strains and different forms of LPS. An immature human MØ cell line (THP-1) was used to investigate NO production in humans. Free LPS failed to produce any measurable amounts of NO from human cells, but produced small amounts of NO from mouse cells. LPS attached to outer membranes and whole bacteria produced significant amounts of NO from mouse cells. LPS attached to outer membranes and whole bacteria produced significant amounts of NO from both human and mouse cells. Human peripheral blood monocytes also produced significant amounts of NO when stimulated with whole bacteria and LPS attached to outer membranes. Macrophages are the principle source of the endotoxin-induced mediator tumour necrosis factor (TNF). This cytokine is pyrogenic and when infused into animals produces all the clinical and pathological features of septic shock. All forms of LPS used stimulated THP-1 cells to release TNF as measured by a L929 bioassay. The characteristics of the production of TNF and NO suggest that a novel pathway independent of CD14 and lipopolysaccharide binding protein might be involved.