Abstract
Previous studies in young rats have reported the impact of 3 weeks of high cocoa intake on healthy immune status. The present article describes the effects of a longer‐term cocoa‐enriched diet (9 weeks) on the specific immune response to ovalbumin (OVA) in adult Wistar rats. At 4 weeks after immunization, control rats produced anti‐OVA antibodies, which, according their amount and isotype, were arranged as follows: IgG1 > IgG2a > IgM > IgG2b > IgG2c. Both cocoa diets studied (4% and 10%) down‐modulated OVA‐specific antibody levels of IgG1 (main subclass associated with the Th2 immune response in rats), IgG2a, IgG2c and IgM isotypes. Conversely, cocoa‐fed rats presented equal or higher levels of anti‐OVA IgG2b antibodies (subclass linked to the Th1 response). Spleen and lymph node cells from OVA‐immunized control and cocoa‐fed animals proliferated similarly under OVA stimulation. However, spleen cells from cocoa‐fed animals showed decreased interleukin‐4 secretion (main Th2 cytokine), and lymph node cells from the same rats displayed higher interferon‐γ secretion (main Th1 cytokine). These changes were accompanied by a reduction in the number of anti‐OVA IgG‐secreting cells in spleen. In conclusion, cocoa diets induced attenuation of antibody synthesis that may be attributable to specific down‐regulation of the Th2 immune response.