The extent of traumatic tissue damage leads to a graded depression of immunocyte function and appears to be amplified by surgical treatment. The endotoxin responsiveness of peripheral blood mononuclear cells displays a functional marker of the anatomically defined severity of injury and gives insights into the regulation of immunocyte function after severe blunt trauma.

Apolipoprotein (apo) A-I is the major protein component of high-density lipoproteins (HDLs), which are responsible for reverse cholesterol transport from peripheral tissues to the liver. A low level of plasma HDL is correlated with susceptibility to atherosclerosis and coronary heart disease . Mammalian apo A-I synthesis has been attributed mainly to liver and intestine . Recently, apo A-I expression has been shown in porcine brain capillaries, suggesting an independent lipid metabolism within the brain . In this study, protein synthesis and secretion were investigated in primary cultures of porcine brain microvascular endothelial cells and compared with those in large vessel endothelium . Active protein synthesis in vitro was demonstrated by metabolic labeling . Cerebral endothelial cells were shown to secrete apo A-I into the culture supernatant, whereas aortic endothelial cells were negative for apo A-I expression . Further studies of transcriptional regulation showed that cerebral endothelium was responsive to apo A-I-inducing agents, such as cholesterol, insulin, and retinoic acid, as previously shown in human hepatoma HepG2 cells . Thus, cultures of porcine cerebral endothelial cells may represent a suitable model for physiological studies of apo A-I-regulation with regard to brain lipid metabolism and blood-brain barrier function . To investigate the interspecies conservation of regulatory elements, 178 by of the 5' flanking region of the porcine apo A-I gene was cloned using PCR techniques . Alignments of the cDNA, of the deduced apo A-I protein sequence, and of the 5' promoter region with the corresponding genomic sequences of different species show a high degree of similarity between the porcine and the primate apo A-I genes, thus indicating a similar function and possibly common regulatory mechanisms in those species . In contrast, the rodent and avian apolipoprotein A-I promoter sequences differed significantly .

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Major trauma leads to the appearance of a circulating inhibitory activity for TNF synthesis that may potentially contribute to an anti-inflammatory response in patients with multiple trauma. The elucidation of its structural and functional properties may contribute to the understanding of the pathogenesis of severely injured patients.