Increasing evidence has implicated gram-negative bacterial lipopolysaccharide (LPS endotoxin) as the portion of the gram-negative bacterial cell membrane responsible for many, if not all the toxic effects that occur during gram-negative bacterial sepsis. The following statement(s) is/are true concerning LPS and the host response. a. The LPS molecule can in itself cause physiologic responses similar to that seen during gram-negative bacterial sepsis b. LPS triggers host macrophages to release a variety of cytokines including TNF-a, IL-1a, and IL-1b, IL-6, and IFN-a c. Excessive cytokine production is not associated with detrimental consequences d. TNFa and IL-1b appear to be the primary mediators within the host, exerting deleterious effects on the host when excessive amounts reach the systemic circulation

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Answer: a, b, d  The LPS molecule exerts diverse effects on the mammalian host. Immunologic responses to LPS include nonspecific polyclonal B-cell proliferation, macrophage activation and cytokine secretion, tolerance to subsequent LPS or bacterial challenge, and production of antibody directed against various portions of the LPS molecule after repeated challenge. Physiologic responses similar to those seen during gram-negative bacterial sepsis occur during LPS administration alone and include hypotension, hypoxemia, acidosis, bacterial translocation across the gut, complement and coagulation cascade activation, white blood cell and platelet margination, and death. Indirect effects result from LPS-triggering of host macrophages. Activated macrophages secrete a wide array of cytokines that include TNF-a, IL-1a, and IL-1b, IL-6 and interferon-a (IFNa). Excessive secretion of cytokines produce substantial systemic effects in the mammalian host. TNFa and IL-1b appear to be the primary mediators within the local host milieu, exerting deleterious effects on the host only after large amounts are secreted and reach the systemic circulation

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