Influence of yogurt consumption on the respiratory immune response

Abstract

The influence of two yogurts, made with different starter strains, on the immune response against a respiratory pathogen was studied. Yogurt P (YP) was prepared with the immune-enhancing strains Lactobacillus bulgaricus CRL 423 and Streptococcus thermophilus CRL 412. Control yogurt (YC) was prepared with L. bulgaricus AV31 and S. thermophilus AV4 strains with no intrinsic immunoenhancing activity. Swiss albino mice were fed YP or YC for five days and infected intranasally with Streptococcus pneumoniae on day 6. The resistance to the infection and innate and specific immune responses were studied. Results showed that both yogurts were able to improve the resistance against pneumococcal infection when compared with control mice. However, YP was more effective than YC in protecting the mice against the infection. Both yogurts improved the activation and recruitment of phagocytes in the respiratory tract, but only YP was capable of increasing the number of IgA cells in the bronchus and the levels of pathogen specific IgA and IgG in the airways and serum. Our results show that the consumption of yogurt is able to enhance immunity in the respiratory tract. In addition, we demonstrate that the protective effect of yogurt could be improved if it is prepared with starter strains of L. bulgaricus and S. thermophils that have intrinsic immunomodulatory activity.