Effects of Probiotic on the Expression of IL-7 Gene and Immune Response to Newcastle Disease Vaccine in Broilers

Probiotics have potential as prevention strategies or therapies for multiple diseases in chickens, such as Newcastle Disease (ND), heat stress, and Coccidiosis, but the mechanism still partially understood. It is an important and warranted issue for further investigation that how probiotics modulated gene expression in disease. In this study, 80 Specific-pathogen-free (SPF) broilers were treated with probiotics, and inoculated La Sota vaccine, then detected the changes of the number of antibody-producing cells (IgA+, IgM+, and IgG+) and the expression of IL-7 mRNA in mucosa associated lymphoid tissue (MALT: Harder's gland, cecal tonsils, duodenum and ileum Peyer's patch), and the content of Immunoglobulins (IgA, IgM, and IgG) in local humor (tear, trachea fluid, bile and intestinal fluid) by immunohistochemistry staining, RT-qPCR, and IELISA, respectively. Results showed that the contents of IgA, IgM and IgG in local humor, the number of IgA+, IgM+, and IgG+ and the expression of IL-7 mRNA in MALT of inoculated birds were significantly higher than control birds (P < 0.05 or P < 0.01) after 7 days post-inoculation (PI), and chickens showed higher immunity response after treated with probiotics. These results indicated that probiotics could enhance the humoral immunity in the respiratory and digestive tracts of chickens, and the immunological response to ND vaccine, and ND vaccine in combining with probiotics will get a better effect on humoral immunity. Both the probiotics and ND vaccine could increase the expression of IL-7 mRNA, and then improve the humoral immunity in the chickens, and the IL-7 maybe one of the ways by which the probiotics improve the humoral immunity.