Different Fatty Acids On Human Neutrophil Immune Function

Background and Objective:In the past few decades, the use of parenteral nutrition has greatly improved the nutritional status of critically ill patients. But the subsequent increasing in infectious complications has became the problem which parenteral nutrition must to face. A lot of researches have shown that, the potential immunosuppressive effects of the lipid composition in parenteral nutrition is closely related to the increase of infectious complications besides other related factors.There are several types of fat emulsion which are the most commonly used in clinical:the soybean oil-based fat emulsion which is rich inω-6 PUFA; medium/long-chain triglyceride-based fat emulsion which is a physical mixture of 50% LCT and 50% MCT; and the olive oil-based fat emulsion which is rich inω-9 MUFA. The purpose of this study is to compare the effects of three different fat emulsions on human immune functions.As the main defense cell of the host immune response, neutrophils present lots of biological behaviors such as chemotaxis, phagocytosis, generating oxygen free radicals and so on. Many aspects such as cell biology, immunology, physiology, pathophysiology will be involved while neutrophils are developing functions and the process is affected by many factors. We can found that the immunosuppression of the neutrophils is mainly presented as the inhibition of neutrophil functions by researching the type of the infectious complications. The purpose of our study is to investigate the effects of three fat emulsions [Intralipid (LCT), Kalu (LCT/MCT), ClinOleic (LCT/MUFA)] composed by different fatty acids on human neutrophil immune functions such as phagocytosis, chemotaxis, and generating oxygen free radicals in respiratory burst in vitro, in order to explore their different influences on human cell-mediated immunity.Materials and methods:50mL peripheral venous blood is collected from each of 15 healthy volunteers, isolate the polymorphonuclear neutrophils (PMN) by the Density Gradient Centrifugation and Lymphocyte Separation Medium, then placed in RPMI-1640 culture medium containing 10% fetal calf serum, adding the above-mentioned three types of fat emulsions respectively, each set up five concentrations (0%,0.01%,0.1%,1%,10%), and cultured for 24 hours. Detect the phagocytosis of PMN by Yeast phagocytosis test, the chemotaxis by Agarose plate test, and the production of oxygen free radicals by nitroblue tetrazolium(NBT) reduction test.Results:1. As the concentration increases, the LCT group and the LCT/MCT group both reduce PMN's phagocytosis. The extent of reduction in the three groups (0.1%,1%,10%) compared with the 0% group have statistically significant differences (all P<0.05). But in the LCT/MUFA group, the extent of reduction is less than the first two groups (LCT/MUFA Vs LCT, P0.1%=0.031, P1％=0.004, P10%<0.001; LCT/MUFA Vs LCT/MCT, P0.1%=0.016, P1％=0.013, P10%<0.001)2. The values of NBT reduction of PMN were significantly decreased in each of the three fat emulsions. The decrease in the values of NBT reduction has negative correlation with the concentrations of fat emulsions, which appears in a dose-dependent way (b=-1.28, P<0.01). Comparisons between the three different fat emulsions show no significant difference.3. As the concentration increased, the chemotaxis of LCT group and LCT/MCT group decrease significantly. With the concentration of 10%, the chemotaxis inhibition rates of the two groups are increased to about 30%, while the LCT/MUFA group is less than 10%(P1=0.005, P2=0.007)Conclusion:In vitro conditions, the fat emulsions composed of different fatty acids can inhibit the immune functions of PMN, including phagocytosis, chemotaxis and generating oxygen free radicals in respiratory burst. The higher concentration of fat emulsion is, the more obvious inhibition is observed. Compared with the LCT/MUFA group, the LCT group and the LCT/MCT group show more pronounced inhibition on human neutrophil immune functions...