Camps-Bossacoma, M. *; Bitlloch-Obiols, M.; Abril-Gil, M.; Franch, A.; Pérez-Cano, F.J.; Castell, M.
Cocoa contains bioactive compounds such as flavonoids, fiber and methylxanthines, mainly theobromine (Katz, D.L., et al. Antioxid, Redox Signal. 2011, 15, 2779–2811; Hurst, W.J., et al. Nature 2002, 418, 289–290). Although many effects of cocoa have been associated with flavonoids (Massot-Cladera, M., et al. Nutrients 2013, 5, 3272–3286), theobromine could also have a role in its effects and this could be reflected in the actions of cocoa on the immune system. Objective: The aim of the present study was to establish the role of cocoa theobromine, in the short term, on the primary (thymus) and secondary (spleen and lymph nodes) lymphoid tissues in rats.
Female Lewis rats (three weeks old) were fed either a reference diet, a diet containing 10% cocoa or a reference diet added with the same amount of theobromine provided by cocoa (0.25%). After seven days of free access to water and chow, thymus, spleen and mesenteric lymph nodes (MLN) were removed to isolate lymphocytes to be immune-stained and analyzed by flow cytometry.
In the thymus, lymphocytes were characterized according to the expression of CD4 and CD8 co-receptors. The proportion of CD4+CD8+ (DP) cells was 95% in the reference group and this percentage decreased in animals fed with cocoa and those fed with theobromine. In addition, both nutritional interventions induced an increase in the proportion of CD4+CD8´ with no changes in that of CD4´CD8+ cells. In the spleen, 10% cocoa diet, and also theobromine diet, significantly decreased the TCRγδ+ and NK cell proportions. Although total TCRαβ+ cell percentage was not modified, there was an increase in the T helper lymphocyte proportion and a decrease in T cytotoxic and NKT cell percentage induced by both cocoa and theobromine diets. In MLN, 10% cocoa and 0.25% theobromine diet induced changes in TCRαβ+ subsets: T helper and NKT lymphocyte proportion decreased and, as a consequence, T cytotoxic cells increased. In addition, both dietary interventions increased the proportion of TCRγδ+ CD8αα+.
These results showed that a 10% cocoa diet and a 0.25% theobromine diet produced the same changes in lymphocyte composition in the thymus, spleen and MLN. Therefore, we can conclude that theobromine is the main cacao compound responsible for the changes in lymphoid tissues.