Obesity development is related to immune system dysfunction promoting the development of inflammatory diseases such as rheumatoid arthritis. High-fat diets rich in saturated and n-6 fatty acids are related to obesity and inflammatory diseases development. These fatty acids have a pro-inflammatory function promoting an excessive activation of immune system. N-3 fatty acids supplementation decreases inflammatory response in these pathologies. However, the effect of high-fat diet rich in n-3 fatty acids was not studied in these models. The aim of the present study is to evaluate the effect of a high fat diet rich in n-3 fatty acids on lymphocyte activation markers. C57BL/6 mice will be fed with control diet (chow) or diets containing fish oil or lard at 40% (HFO and HL) (wt/wt) for four weeks. After the period of supplementation, arthritis will be induced by bovine-type II collagen (200 ¼g) and the same quantity of complete Freund's adjuvant injected intradermically through the tail. Twenty one days later, bovine type II collagen and the same quantity of incomplete Freund's adjuvant will be injected again. After arthritis installation, mesenteric lymph nodes will be removed and lymphocyte isolated. Afterwards lymphocyte proliferative capacity will be evaluated by thymidine incorporation and concanavalin A stimulation. The percentage of T regulatory cells (CD4+, CD25+, Foxp3+) will be determined by flow cytometry. Expression of activation (CD25 e CD28) and suppression related molecules (CTLA-4 e CD95) in T lymphocytes will be determined by flow cytometry.
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